[black.jack] n (1591) 1 [black + jack (vessel)]: a tankard for beer or ale usu. of tar-coated leather
2: sphalerite
3: a hand weapon typically consisting of a piece of leather-enclosed metal with a strap or springy shaft for a handle
4: an often scrubby oak (Quercus marilandica) chiefly of the southeastern U.S.--called also blackjack oak
5: a card game the object of which is to be dealt cards having a higher count than those of the dealer up to but not exceeding 21--called also twenty-one, vingt-et-un
[2]blackjack vt (1905) 1: to strike with a blackjack
2: to coerce with threats or pressure