A person whose entire life revolves around one
thing and who is perfectly happy remaining ignorant of real life and the outside
world.
Like how a fish is perfectly happy inside of their bowl, not even caring that there is an entire ocean out there.
Jeremy is such a fish. All he does is go to the
gym, talk about the
gym, eat at the gym, and
think about the gym. Does he do anything else besides the gym? No, because he's a fish.