Noun

• S: (n) blackjack oak, blackjack, jack oak, Quercus marilandica (a common scrubby deciduous tree of central and southeastern United States having dark bark and broad three-lobed (club-shaped) leaves; tends to form dense thickets)
• S: (n) blackjack, cosh, sap (a piece of metal covered by leather with a flexible handle; used for hitting people)
• S: (n) black flag, pirate flag, Jolly Roger, blackjack (a flag usually bearing a white skull and crossbones on a black background; indicates a pirate ship)
• S: (n) blackjack, twenty-one, vingt-et-un (a gambling game using cards; the object is to hold cards having a higher count than those dealt to the banker up to but not exceeding 21)
• direct hypernym / inherited hypernym / sister term

Verb

• S: (v) blackmail, blackjack, pressure (exert pressure on someone through threats)