A person who eats fish but no other kinds of meat. Commonly referred to as "vegetarian".
"Yeah, I'm a vegetarian, but I eat fish." "Well, then you're not a vegetarian." "What am I, then?" "Officially, you're a lacto-ovo-vega-vegavore. But you can call yourself a pescaterian." "Terrific!"
1: pescaterians are people who eat no meat other than fish.
2: pescaterian is a slang term for a lesbian, this is because licking pussy can be likened to a hunger for fish.
Guy 1: Dude, this women looks so butch.
Guy 2: She must be a pescaterian.