be at it(redirected from been at it)
be at it
1. To partake in an action, activity, or pursuit vigorously, exhaustively, or determinedly. I studied really hard for this test; I was at it all night. I wish those dogs would quit barking, they've been at it since the sun came up!
2. slang To engage in sexual intercourse. I can always hear when the neighbors are at it. It's really embarrassing!