Source : WordNet®

blackjack
     n 1: a common scrubby deciduous tree of central and southeastern
          United States having dark bark and broad 3-lobed
          (club-shaped) leaves; tends to form dense thickets [syn:
           {blackjack oak}, {jack oak}, {Quercus marilandica}]
     2: a piece of metal covered by leather with a flexible handle;
        used for hitting people [syn: {cosh}, {sap}]
     3: a gambling game using cards; the object is to hold cards
        having a higher count than those dealt to the bank up to
        but not exceeding 21 [syn: {twenty-one}, {vingt-et-un}]

blackjack
     v : exert pressure on someone through threats [syn: {blackmail},
          {pressure}]