1. noun, slang A shortening of "fraternity," a social organization for male undergraduate students. I have no plans to join a frat in college—that lifestyle just doesn't appeal to me.

2. adjective, slang Relating to such a group. I went to a frat party last night, and it was pretty lame, honestly. If you're looking for Mike, you might want to check the frat house—he's usually there in the afternoons.