Punk is a slang term used in prison to describe
homosexuals. Typically in prison
you wouldn't say "That guy over in 5 cell is gay" you'd say "The guy in 5 cell is a punk".
Usually during intake CO's will ask you questions about gang affiliation, sexual identity,
suicidal thoughts etc and separate you in to tanks, pods, or dorms where they think there will be the fewest incidents because of your status. As a result they will put homosexual people together and the dorms they're housed in are called "punk tanks"