Techinically a person who eats no meat or dead animal products. Some choose so for ethical reasons while others may simply be grossed out by the prospect of eating flesh. Despite claims to the contrary, most vegetarians are not elitist or prejudiced. Another false argument also includes that eating only plant matter kills more rodents, etc which it doesn't. In order to eat beef for instance, it takes far more energy and resources to grow food for them (as opposed to eating it directly) and then killing the cows on top of it. There've been many proposals for third world countries to focus on farming as opposed to ranching because, if done properly, it takes far less resources and land space. Another common argument is that it "destroys your body" which is blatantly false. It's actually very easy to get sufficient amounts of protein as well as other nutritional necesseties. While in the past it may have been necessary to eat animals to get by, many argue that it no longer is. Our canines are a "left over" so to speak of our evolution in the past.
Despite all this, and despite that most vegetarians are non-judgmental and aren't affiliated with PETA in anyway, many get a good dose of humor out of bashing them. Presumably because the concept of not eating meat challenges their manhood and they need to defend their metaphorical dick size.
I've been a vegetarian for years, since I was 16. The rest of my family has always eaten meat but I (like most others) don't hold it against them. But you can't convince the morons of that.
*at dinner with a group of people*
Person A: Yeah, I'll have a vegetarian burrito please.
Person B: OH GOD. Oh what, are you a VEGETARIAN? Huh? You think you're too good for us?
Person A: Uhhh, no.
Person B: Yeah, I can see it in your eyes! You're not gonna stop the rest of us I hope you know!
Person A: You knowwww.... I really didn't plan on it. Eat what you want; it's your choice.
Person B: I told you you can't stop us! GOD, what is it with you people?! I'll bet you're a FASCIST too aren't ya? And a faggot. GOD, you make me sick. I bet you just can't STAND the thought of me eating a steak, can you? Huh? HUH?
Person A: Wow, you're an idiot.