From Longman Dictionary of Contemporary Englishknock it offknock it offspokenSTOP DOING something used to tell someone to stop doing something, because it is annoying you → knock
Examples from the Corpus
knock it off• And, how was it, no, if they knocked it off.• I knocked it off as I ran past.• The following day we could knock it off in few hours before returning to base.• You kids, knock it off in there!• No, you didn't have to knock it off you had to choose thingies on a card. 