JOKER

n. 1 a person who jokes. 2 sl. a fellow; a man. 3 a playing-card usu. with a figure of a jester, used in some games esp. as a wild card. 4 US a clause unobtrusively inserted in a bill or document and affecting its operation in a way not immediately apparent. 5 an unexpected factor or resource. the joker in the pack an unpredictable factor or participant.