Would that one could count on hard definitions for things… 
It’s a useful characteristic for technical matters, for the rest of life it just gets in the way.
My personal preference. I like chicken and other poultry as much as the next guy, but that being the only source of meat in my diet would get boring awfully fast. Same thing with pescatarian, and I love fish.
YMMV. 
When I was watching the vegan youtube channels, many of them changed to calling their diets plant based because of the drama that the vegans were causing. The vegans were accusing other people and each other of all kinds of things. The infighting got nasty.
The youtubers who wanted to move away from the drama started calling their new group plant based to move them away from their vegan counterparts. It didn’t mean anything, really. It just meant that vegans were getting an ugly reputation, so some people wanted to differentiate themselves to move away from that.
Some folks who eat a lot of meat are awfully touchy about other people choosing to eat less or none.
I love the taste of meat and other animal products, especially cheese. But knowing the conditions in factory farms, I don’t feel good about supporting them. And I realized long ago that there are lots of vegetarian/vegan foods I enjoy, and that sometimes when I ate meat it wasn’t because I specifically wanted it, but because it was there; it was the default. I didn’t feel like I could go completely vegan forever, but I could cut back by at least 80% pretty painlessly. And that’s what I’ve done. I now default to vegetarian/vegan options, but make exceptions when it makes sense to me to do so-- such as when I’m traveling and veggie options are limited, or when my husband really wants to share his favorite foods with me, or when I’m just really, really craving cheese. I think “plant-based” is a pretty good descriptor of my diet.
People’s reactions to my choices tell me a lot about them.
Is it really hypocrisy?
Is it hypocritical of a vegetarian, to, say, eat a couple bites of turkey on Thanksgiving to avoid offending the in-laws, but not any other time of year? Is it hypocritical of a diabetic vegan having a low blood sugar episode to eat some milk chocolate to stave off collapse when there is no readily available alternative?
I don’t expect perfection from other people.
Now, if they call themselves vegetarian but eat a beef burger every Sunday, yeah, I’ll look at that a bit sideways but you know what? Not really any of my business. I’d call that “flexitarian”, perhaps, but again, not really my business.
I know two - they’re both allergic to dairy so that makes a lot of sense.
That’s what I described. It’s hypocrisy. The chances of that actually mattering to me are pretty low though.
Some vegans might or could (and do?) eat things like accidental road kill because it is seen as ethical to do so. This is because veganism is not a diet but a philosophical outlook where adherents avoid as much harm as possible to animals and others that can suffer or feel pain, to an extant that is reasonable and practicable. Even if this will often result in a strict vegetarian diet (at least in developed nations), something like cultured meat might be allowed to be included if and when it is available (and palatable 
).
So no, being a vegan doesn’t automatically mean you don’t eat or use any animal products. Very few vegans would forgo using medication that is derived or tested on animals if they need said medication to live, for example, and very few vegans would starve themselves on a desert island if they could only survive there by eating (some) animals, IMO.
Nitpick, but a flexitarian is not someone who mostly or mainly eats vegetables, but plants!
In addition to vegetables, plant foods include fruits, nuts, seeds, grains and spices.
Mushrooms are not plants but few if any vegetarian will not eat them unless they just don’t like the taste, not due to any moral or health concern, since that would be quite silly. Mushrooms are very healthy (unless you would really like to eat death caps or something )! Technically, pretty much every strict plant-based diet should probably be called plant-and-fungus-based diet, but that might sound kinda gross? 
If the only alcohol I imbibe is a glass of sparkling wine once a year, am I “a person that drinks alcohol”? Or am I a smoker if I smoke one cigarette a year (and not anything else)? If not, how often would I have to to be considered either one?
How about getting fall down drunk every Friday night? How much clearer do I have to be, I’m talking about people who claim not to do something but still do it any time they feel like it. And they are not likely to honestly admit that.
Many carnivores in the wild obviously have diets that are 100% animal, so obviously there are non-plant-based diets. Even some humans, like Jordan Peterson and his daughter, went or are on a non-plant-based diet of only salt, beef and water. A monotrophic diet.
That was in response to the definition of plant-based as not exclusively plant-based, which includes non-plant-based diets as well. It’s not a good way to define something.
Some vegans used plant-based to mean strictly so. Some non-strict vegetarians use it also. So yeah, it’s a messy situation.
I guess I’ve been out of the loop! 
I’m all for eating healthy and environmentally sustainable, but I wish people didn’t get so aggressive about what they eat.
There’s a Suzuki-roshi anecdote from the '60;s, told by a guy who was driving him somewhere, probably to the zen monastery he founded at Tassajara in Big Sur. The guy was a zealous vegetarian (zen monasteries are typically vegetarian), so when they stopped at a diner to get something to eat he was chagrinned to find almost nothing he could eat on the menu. He finally ordered a grilled cheese sandwich, and Suzuki ordered a double hamburger. When their food came, Suzuki grinned at him and said, “Let’s switch!”
Guy said he was never really attached to his vegetarianism after that, the way he had been before.
Sorry, I’m not very smart. 
Okay, I totally agree that people who claim to be X but still frequently do something that is against X, while simultaneously claiming to never do anything against X, are hypocrites. I don’t know how many hypocrites there are when it comes to vegans and vegetarians.
The interesting thing (to me!) happens when that thing they do that is against X is extremely infrequent.
For example, if I tell my friend that I don’t drink, but said friend sees me drinking a glass of beer at a new year’s party, they might think that I’m a hypocrite or that I stopped being a non-drinker. But if they asked me about it I might say that this is the one drink I have all year. Does or should that change my friends view of me after that?
I guess that will depend on why I don’t drink. If I think drinking is extremely immoral, that might be a little hypocritical if I did it (unless I changed my mind), even once. But if I just decided to never drink because of health reasons or something then maybe not so much, if at all.
I think the same might apply to people adhering to plant-based diets. If someone is on one due to health reasons, I don’t think you really are a hypocrite when you eat a steak once a year. But if you are one due to moral reasons, a stronger case could be made that you are a hypocrite.
I think much of this pushback on @TriPolar can be tabled if we recall this is how he described himself:
Moving on…
“Plant based” was never intended to mean “primarily plants” or “mostly plants”, it was always a label for a diet that a vegan would recognize as a vegan diet. It is a poorly named & ambiguous label which is unfortunate but many things in life don’t have the best labels.
If you go into a store, items either a) have large and obvious amounts of animal products, b) have small, unrecognizable trace amounts of animal products or c) contain no animal products. The primary challenge vegans face is being able to distinguish b from c. Thus, labels such as plant based are useful to distinguish that something is c and not b. It makes no sense for there to be a label that is ((b & c) but not a) since that’s not a challenge anyone faces when shopping.
I was wondering if that was just me since there was a time when I called myself a vegan (still do but I’m careful about the audience), so I might be sensitive about it. But I just did a search on 'vegan bad reputation" and got pages of articles about it.
Fair enough. What I meant is people who generally/limit consumption of animal flesh and products (i.e. mainly follow some form of a traditional vegetarian diet), but will eat animal flesh on occasion. Also known as “semi-vegetarian.”
I think you are right. I was out for lunch with friends at my last job and we were picnicking and had a bunch of stuff, including some sushi with egg [tomagozushi, my favorite] and she had a piece. One of her friends had been passing by and absolutely rounded upon her and made such a ruckus that Tina was red with embarrasment. Over the equivalent of a single egg. What the 4 of us sitting there lunching understood was Tina ate pretty much exclusive vegan because of her then boyfriend - but actually was an omnivore. The asshat was a friend of her BF Jamie, and obviously was a rabid vegan type.
I tend to eat plant based, probably 80 percent or so veg/grain/fruit/pulses. I also happily eat anything that won’t eat me first as long as I am not allergic to it, though I admit I hate both octopus and squid, and uber fishy fish [like eel, mackeral, sardines. Tastes and smells to me like it has been rotting on the seashore before they picked it up to serve me. No idea, perhaps some sort of companion allergy related to my shellfish allergy?] Just like being diabetic and being ‘caught’ eating a piece of cake [I plan for an occasional indulgence. My endo and nutritionist gave me a rough nutrition plan, with a 180 calorie ‘random’ daily allowance for a treat. I could sit there and eat sugar out of a bag with a spoon if I damned well wanted. I tend to just fold my treat calories into my normal plan. ] I have had people at my various jobs that thought I was some flavor of vegetarian and would ‘get caught’ eating meat. WHat I eat is my own damned business, not anybody elses.