A person that does not eat any meat apart from fish that eat fish.
A diet that is mostly vegetarian but allows only the consumption of fish that eat other fish.
Waiter: Here is your fish sir.
Pesca-pescetarian: I'm sorry , this is not a cannibal fish. You see, I'm a pesca-pescetarian.
A: Would you like ham and lamb on your pizza?
B: No thanks, but chicken and fish will be fine.
A: Why, are you some sort of bird eating, fish eating vegetarian or something?
B: Pesco-pollo-tarian, baby!