doubleton
/ˈdʌbltən/noun
1- (in card games, especially bridge) a pair of cards which are the only cards of their suit in a hand（桥牌等牌戏的）双张（指一手牌中某花色仅有两张的牌）。
1.1
- as modifier denoting a card which is one of a doubleton双张中的一张：
a doubleton ace
双张爱司。
1.2
- a pair of people or things（人或物的）一双, 一对。
词源
early 20th cent.: from DOUBLE, on the pattern of singleton.