Short for Temporary Speaking Ban. A kind of unilateral jinx, which prevents a person who just came out with a really shit joke speaking for around five minutes.
Five minutes is a rough guide - to be honest, the first time you speak after a temp ban is inviting people to resume belittling you with comments like "aren't you on a temp ban for coming out with shit like that?" and punching. You're better off just starting with a clean slate the next day.
Even worse jokes can result in a perm ban, which is valid for the remainder of the unfunny prick's academic life.