I ordered the Cajun Pasta, all shrimp (that is, with extra shrimp replacing the chicken and andouille sausage), and the server asked, “Are you a vegetarian, or do you just like shrimp?” As it happens, I just like shrimp. But I noticed the word vegetarian, used here to refer to someone who doesn’t eat red meat or poultry but does eat seafood — a usage that annoys strict vegetarians mightily.
What’s at issue here is superficially a matter of language, but at root has to do with categorization, in this case the categorization of foodstuffs. There’s a folk taxonomy here, in which the flesh of animals (in the broad sense of animal, as in “animal, vegetable, mineral”) is distinguished from food from plants, and within the FLESH category, the flesh of mammals (RED-MEAT) and birds (POULTRY), taken together (as MEAT), is distinguished from sea creatures used as food (SEAFOOD), and within the SEAFOOD category, there’s a division into FISH and SHELLFISH.
This is a folk taxonomy, not a scientific one, and like folk taxonomies in general it’s imperfect. The labels I’ve given, in all-caps, are just (suggestive but ad hoc) names for the categories, not expressions used by English speakers to refer to these categories. (Taxa in folk taxonomies don’t necessarily have ordinary-language names.)
The question is then how ordinary speakers of English talk about these matters.
As usual, there’s a lot of variation, and a certain amount of disputation about usage.
Many speakers of English reserve the word vegetarian for reference to people who do not eat things in the FLESH category (including SEAFOOD). But some (like, apparently, the server in the vignette above) extend the word to take in the eating of things in the SEAFOOD category. For this, some people use pescetarian (or pesco-vegetarian or piscatorian).
A certain amount of confusion is sown when vegetarians (in the narrow sense) tell people that they “don’t eat meat” — and then risk being served fish, because, as their hosts explain, “fish isn’t meat”. Some time ago I learned not to say of (strict) vegetarian friends that they didn’t eat meat, and opted to say that they were vegetarian. But now I see that this won’t do either, and I’ll have to say that they don’t eat meat or fish.
In any case, the MEAT category (excluding SEAFOOD) plays a role in our culture, at least for those who are familiar with religious bans on “meat” on Fridays or during Lent. Fish, however, was fine, and meals on “meatless” days tended to involve eggs, cheese, or fish.
Meanwhile, for many people in many other contexts, meat denotes the category I’ve labeled RED-MEAT: beef, veal, lamb, pork, venison, rabbit, etc. In a discussion on the American Dialect Society mailing list last November, several people suggested red meat as the label for this category, but many are reluctant to call pork or rabbit (or, sometimes, veal) “red meat”, especially given the advertising campaign to market pork as “the other white meat”.
To make things more entertaining, the Wikipedia entry for Red_meat gives two technical usages:
Red meat in culinary terminology refers to meat which is red-colored when raw, while in nutritional terminology, it refers to meat from mammals.
CULINARY-RED-MEAT then excludes pork, rabbit, and veal while taking in duck and goose, so it’s far from RED-MEAT. The nutritional definition, however, picks out the RED-MEAT category.
(There’s always some indeterminacy in these things. Goodness knows what people do with turtle meat, alligator meat, frog, snake, etc. I assume that they’re not acceptable to ordinary vegetarians, nor would they be acceptable on “meatless” days. But if your doctor tells you to “avoid red meat”, are they in or out?)