I do it to show off and make other people feel stupid. Is it working?
I do that, when, for example, I’m speaking to children and old people. When I’m speaking to another normal adult, I don’t assume that they’re linguistically deficient. If they prove to be so, I can adapt. But it’s a “them” problem, not a “me” problem.
**Why do (smart) people use big words? **
Do We?
I use big words because, in most cases, I don’t realize they’re big. I read rather voraciously as a child and teen - exclusively fiction, mind you, so I wasn’t picking up technical lingo, at least not deliberately. Regardless I still stumbled into having a pretty large vocabulary and not having any fear of any of it. So I use it, and don’t really notice that I’m doing so.
Perhaps interestingly, I have generally not been chided for using long or unusual words, probably because my family and friends are all pretty smart, even those who are not well-read. The one exception is at work - I’ve occasionally been jumped on for using a word that my co-workers flatly deny is real. (Education generally ensues shortly thereafter.) But aside from that, I’ve received relatively little negative reinforcement for my linguistic tendencies.
So yeah, most of my large words are just that: words that by sheer coincidence happen to be large. There are a few exceptions - long words that I use because they’re fun. Defenestration is a great example of a word I use sheerly for its cromulence.
Doo wah diddie diddie wah diddie doo.
That’s really the point. Big words don’t (necessarily) come from smart people. They come from people who read a lot. People whose vocabulary is essentially the sum of the vocabularies of every author they read.
Which just moves our topic question to: “What kind of people read a lot and retain at least some of what they read?”
The answer may not be smarter people, though few real dummies read for pleasure. But it is IMO more curious people. People who want to learn or experience, even if the thing they’re learning is fantasy magic or art or cooking, not real world science, history, or politics.
Ultimately, if one reads a lot of stuff written by professors one starts to sound like a professor. If one reads lots of stuff written by Trump one starts to sound like Trump. If one reads lots of stuff written by poets one starts to sound like a poet.
And if one reads nothing, one also sounds like Trump.
Speaking as an experienced amateur smart person: I like words. They are the tools of one of my arts. They don’t have to be long, just interesting and exact. Intellectual curiosity reads as pretentiousness to many who aren’t. I am not being pretentious, in the sense I am trying to influence anyone’s opinion of me, an activity which has always bewildered me. This is just how I talk. To everyone.
I use bigger words sparingly and with the right audience. My day-to-day speech is pretty standard. When I talk to certain subsets of people, my vocabulary range changes a bit (perhaps an example of code-switching.) I don’t think of myself as a “big word” aficionado, but sometimes there is a single word that so neatly describes and connotes a concept I have in mind that I use it with the right audience–and that word is, quite often, a so-called “big word.” And with some people, I just use it for fun, as a bit of a game. I have a friend who tutors SAT with whom I’m like that with.
So close!
That’s a good one. And in the proper location, nothing beats sesquipedalian.
Long words can also flummox nagging two-year-olds. With the warning that they will be onto you by the time they’re four.
I dunno. “Defenestration” is like the Millard Fillmore of big words–the one that everyone knows because it’s delightfully obscure. Well, that and the Defenestration of Prague for the history buffs.
Some people are just magniloquent by nature.
'fraid not. Sorry.
I don’t want to be a pompous twit, so if you can tell me a short word for “photosynthesis” I’ll gladly use it.
Otherwise, I’ll just be pretentious and use the big word.
Well, I’ll be superamalgamated.
Best be careful with that. They will be picking your nursing home and they have very, very long memories. 
This, more than “social circle” I think. And FWIW the comics (the books more than the strips perhaps) in my had some pretty high end vocabulary too.
The problem however with having developed the vocabulary by reading is that one can get the pronunciation wrong when speaking it, even if it comes naturally as the word to use. I used to do that and it was a bit embarrassing.
Another vote btw expressing admiration for those with the level of smarts that they know and think in the longer or more obscure words that communicates that which would otherwise take a sentence and does so with precision but who are skillful enough at actual communication that they correctly assess and know how to play to the room they are in.
Subject-verb agreement is where you really separate the sheep from the goats.
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should be “words that communicate” (singular)
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should be “those…[who] do so with precision” (plural)
It’s a run-on sentence, but here it is rewritten anyway: Another vote btw expressing admiration for those with the level of smarts that they know and think in the longer or more obscure words that communicate that which would otherwise take a sentence and who do so with precision and who are skillful enough at actual communication that they correctly assess and know how to play to the room they are in.
Cite: Zippy.
Words are a toolbox, some people can get by in life with a can of WD-40 and a roll of duct tape. Other people have a garage full of tool chests with some of the most incomprehensible and exotic paraphernalia you’ll ever see. You can make do with very little but sometimes you need the right tool for the right job.
Plus, as a self professed word nerd, I’ve been lead to believe that the ladies love a huge vocabulary. SWMBO laughed the first time I told her I had one, so it must be true… 