A person who chooses (for ethical, religious, health, or personal reasons) to abstain from eating the flesh of animals.
Vegetarians tend to be thinner, healthier, and have less body fat than meat-eaters. This is because many vegetarians realize the health benefits to eating a purely meat-free diet and adopt other healthy habits (no smoking, no excess alcohol, regular exercise, etc).
Contrary to popular belief, vegetarians are not preachy. You do not need to 'feel bad' about eating meat around them. They have usually made the choice for themselves and live a peaceful lifestyle that doesn't involve forcing their beliefs down other peoples throats.
Would you like a hot dog?
No thank you, I'm a vegetarian.
Oh okay, we have some veggie burgers if you would like one.
Yes, thank you very much!