Bastardization of vegetarian used for dry humor. The idea is that the user has never heard of vegetarianism and thinks he is inventing the word for it when somebody says that they don't eat meat.

The humor comes from oversimplification, implied ignorance, and laughable wordcoinning. It also kinda sounds like Unitarian, implying a quasi-religious respect for vegetables.
Dude: Have some chicken fingers.
Loser: I don't eat meat
Dude: Chicken is barely meat.
Loser: I NEVER eat meat, I'm a vegetarian
Dude: Oh, so you're like a vegetableitarian?
Loser: ehhh...I guess.
Dude: Sorry, I didn't mean for you to go against your "religion"
Loser: (huhhh?)
by TreeWeezel April 9, 2011
Get the vegetableitarian mug.