blackjack

(noun) 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. Synonyms: blackjack oak, jack oak, Quercus marilandica.

(noun) a piece of metal covered by leather with a flexible handle; used for hitting people. Synonyms: cosh, sap.

(noun) a flag usually bearing a white skull and crossbones on a black background; indicates a pirate ship. Synonyms: black flag, pirate flag, Jolly Roger.

(noun) 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. Synonyms: twenty-one, vingt-et-un.

(verb) exert pressure on someone through threats. Synonyms: blackmail, pressure.