1. (verb)blackjack, cosh, sap a piece of metal covered by leather with a flexible handle; used for hitting people Synonyms: sap, black flag, fool, saphead, jack oak, blackjack, vingt-et-un, muggins, pirate flag, tomfool, twenty-one, cosh, blackjack oak
2. (verb)cosh hit with a cosh, usually on the head