a variety of rummy in which a hand with unmatched cards totaling no more than 10 points may be exposed: the hand exposed wins or loses points, depending on whether the opponent's unmatched cards add up to a higher or lower total
See gin rummy in American Heritage Dictionary 4
noun
A variety of rummy for two or more persons in which a player may win by matching all his or her cards or may end the game by melding with unmatched cards that add up to ten points or fewer.