No, you don't have to use the dictionary definition

I dont think there’s anything wrong with defining your own special version of a term, upfront, just so you can refer back to it succinctly in whatever you say right after that, but you will often encounter people who dont want to let you do that because they have a fixed idea of what the term should really mean. Often their version is just one of many possible versions, but they’ll derail the whole discussion with arguments about it.

What is controversial here?

If an individual is using a word or term differently than the vast majority of listeners in their specific intended audience understand the word or term to mean, then that is failed communication, whatever the dictionary states.

One cannot just mid discussion define “blue” as the color of apples and embarrassed cheeks and blame misunderstanding on others not realizing you were using the word in an unconventional manner.

And interrupting a discussion to opine what “literally” means, or that it should be “rein” not “reign” is obnoxious.

It’s the same point as in the descriptivist/prescriptivist threads: know the room, and try to understand what was intended to be communicated.

Looking at the thread the OP pretty quickly clarified what concept they were trying to communicate and methinks arguing over the definition of “fifth column” was really a bit silly.

Not everyone gets this. This problem has existed for centuries, probably millennia. Definitions are tools, lexicographers rely on usage panels not divine mandates, you don’t have to use any particular definition: you just need to be clear.

I think you can, as long as you’re transparent about it.
Blue apples would be a stretch, but its an example that is perhaps way more incongruous than the things that happen in day to day debate. I imagine you chose that for emphasis of your point - reductio ad absurdam - but most cases where definitions are argued, the case is way more subtle and nuanced than blue apples.
If someone in the apple industry wants to coin the term ‘blue apples’ to mean something specific (I dunno, maybe some set of varieties with a greyish waxy bloom on them), we cant stop them, and we just sort of have to accept that terminology.
They have to accept being faced with confusion and argument if they use that term with people outside of the context where it is familiar, or accept the burden of prefacing an explanation of the term.
There are blue horses and blue dogs that are not actually blue, so this is not a new thing.

Which is then a failure of effective communication.

To be sure words can be used in novel ways, analogies can made, and not only understood by all involved but have their usage take off. That happens all the time. But if a discussion is mired down in arguing over the definitions then effective communication is not happening.

This is an aside but there are good reason why “blue” works for some dogs that are not really blue. The same reason why some humans got called white, some Black, and even if not proper nowadays, some yellow, even when none actually are those colors: relative to each other in the universe of skin tones they work as a sort of geometric transformation on the color spindle. (“Red” fur in the dog world also is not really red, only relatively so.) It did not happen because one person arbitrarily defined the term and others said “sure.” It happened because it fits with how our minds work.

It is, but its not necessarily reasonable for people to anticipate every way in which things very familiar or obvious to them may be unfamiliar or obscure to others. Sometimes you do your honest best to communicate and you may still be met with confusion that you have to clear up.

And thats especially true of somewhere like an internet message board with members from all over the world - its not as if you can even predict who the audience will be. And if you try to work around that by explaining everything, thats also ineffective communication on the grounds its probably too much.

I think many words get used colloquially or lazily.

E.G. Many will say what is happening in Gaza is genocide when it is ethnic cleansing. Both are certainly bad things but they are not the same thing at all. Bringing it up seems like nitpicking or trying to minimize what is happening but those two are distinct concepts and worth distinguishing.

Pointing to the dictionary definitions clearly shows they mean different things and it is not amiss to point that out.

Agreed. So let’s look at the thread that spawned this and constructively criticize how that could have gone better.

The OP used a phrase to try to communicate a concept. At least one person did not completely understand what the OP intended to mean, and asked for clarification.

The OP then clarified what they meant when they used that phrase, what their proposition was. The conversation then began to proceed based on that clarification.

That was as it should be.

Another poster coming in to harass on what they saw as an improper use of a phrase in the OP, which happened next? Not as it should be. And off the rails it goes, arguing the definition of the phrase instead of the intended debate. But but words have meanings! He used it wrong! Make it stop!

That part is not good faith effort at communication and discussion. It’s rigid prescriptvism not accepting a win and perseverating.

And this illustrates why it isn’t okay to unilaterally define a word or phrase and just be perplexed when confusion or argument results.

Starting an argument about whether the definitions presented are correct marks you as a newbie to philosophy or rhetoric. Or a midwit. Most of us have been there at one time or another. I agree that communication can be effective or ineffective.

“In the following essay I will establish X. To do so I will define the following 12 terms as their first antonym as listed in The Dictionary of Antonymns, 5th edition.”

That very well could be a valid argument. It would be very poor communication though. Generally speaking, it’s better to discuss the substance of the underlying argument instead of its expression, but that assumes the reader hasn’t already thrown up their hands.

ETA: Whack-a-Mole provides a good counter-example. Well done (setting aside the international relations part of his claim, which is extra-topical to this thread). But I still think it’s acceptable to define a word in non-conventional ways provided you state the implications of that up front and why you are doing so. Doing so takes care not to mislead your audience.

ETA2: I wrote that before seeing the next post. ETA3: Put it back Whack-a-Mole! It’s a good point.

I put this back by request (took it out after seeing @Measure_for_Measure 's reply to my previous post but put it back):

What if the person you want to argue against is poisoning the well by using incorrect definitions? You either need to tackle those definitions or debate on their prepared ground and terms. It doesn’t seem reasonable to me to accept that debate on their incorrect terms and it is entirely correct to show that their very premise for the debate is fallacious (or at least rhetorically charged to tilt the debate).

The dictionary is great when encountering unfamiliar words.

Perserverating is a real word! I would have have corrected that to persevering. But I looked it up first.

per·sev·er·ate

/pərˈsevəˌrāt/
verb
Psychology
gerund or present participle: perseverating

  1. repeat or [prolong]
    repeat or prolong an action, thought, or utterance after the stimulus that prompted it has ceased.
    “they perseverate under stress”

I wonder two opposing things.

How many people do check a dictionary (Wiki may be more useful at times) for guidance on words or terms they are unfamiliar with. And how many don’t.

I suspect that some people in the other thread had no real idea about the history and usage of “fifth column” and were simply repeating the mistakes of others.

No good solution is readily at hand for either problem. And so threads go down the drain.

100% agree. Hence why the OP’s response was laudable. They dropped the phrase immediately and went long hand to explain what they meant.

And an aside, maybe even blurred, about that would have likely been read with interest by those of us like me, who have heard the phrase but were actually ignorant of its origin. A separate thread could also be born debating if its current use is generally understood to be that precise historical bit, or more broadly, and if so how broadly. (And I could avoid that one!)

Bonus tip: dictionaries vary in quality. Merriam Webster is different than Webster. Merriam Webster is cheaper and significantly worse in quality than eg Webster’s New World College Dictionary. Splurge on the latter - less than $15 on Amazon.

For example, Webster’s has a lot helpful usage notes which provide distinctions between closely related words.

Also, the first definition isn’t always the most common definition. In Webster’s case, definitions are placed in historical order.

My go-to is the Oxford English Dictionary. Unfortunately, it ain’t cheap (over $1200) and it is quite big (20 volumes). My dad had a version which had four pages on each page. It was still two volumes and they came in a case that had a magnifying glass in the case so you could read it. Really cool.

But, to my mind, it is the authoritative English dictionary.

The worst is Google (IMHO).

YMMV

The Compact OED you’re referring to was given out as a ridiculously cheap premium for subscribing to one of the book clubs (either Book of the Month or the Literary Guild). That’s how I got mine, and the only way I could have afforded it at the time.

Nobody should get the print edition, and I say this as a print diehard. The linked website reminds buyers that even this set was the Second Edition and Supplements from 1989, several generations ago in dictionary terms.

The Third Edition OED is strictly online, which allows them to enter new words and meanings all the time rather than wait years for supplements. It is a work in progress since a full unabridged version will never be issued in print again. Access to it requires a subscription, currently $100/year in the U.S.

I dunno.

Yeah, it may be old but, like you, I am a print diehard. And, frankly, I suspect 99% of it is the same as today. I do not know but I’d hope buying it would get you a subscription to the website too.

There’s just something so elegant and cool about the print edition if you can still get it.

I think sometimes we do need to adhere closely to definitions even if “dictionary” may not be the right word.

Some arguments use such a combination of socially-charged and nonstandard definitions that the conclusions, if agreed to, sound preposterous to those speaking standard English. The most non-controversial example I can think of is the proofs of God that don’t assign it any particular characteristics that are reminiscent of an intelligent being, much less anything approaching the Abrahamic God. Even if you agree that the argument is correct given the definition, you are not going to agree with the conclusion “Yes. God exists.”

Now, I don’t think that this is a particularly harmful argument. While religion is the cause of a lot of harm, the argument is preposterous enough that it won’t convince anyone who doesn’t already believe in God. Not necessarily so for people who want to use nonstandard definitions in a variety of other social dialogues.

I was unable to come back to my thread on MAGA being a fifth column until last night due to work. After catching up on the evolution of the debate, I spent some time composing a pit thread using words like pedant, specious, and fallacious. I made sure to use all the words in a slightly incorrect way in hopes it would needle some posters (and I am not referring to sewing together black-light wall art here). I then talked about hair-splitting and treatment using conditioner, well-poisoning and EPA attempts to regulate it, fault-finding and other methods used by geologists, and nit-picking and other common treatments for crabs (and yes, I know that P. Pubis is technically not a crustacean, but a louse). I then rounded out the thread with a discussion of pettifoggery and that one does not necessarily need to be a lawyer to engage in it while point to some recent examples.

I then found this thread.

While amusing to me (my jokes are always the best!), I realized that this thread was a better response to the hijack of my MAGA debate topic that what I had written. I felt taunted, and you all talked me down with the discussion here. You guys are great. I especially want to thank @DSeid for his vain (and no, I am not making any comments on your opinion of yourself) attempt to get my thread back on track. You showed much more patience than I could ever be capable of.