"blackjacks" in the noun sense
1. 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
2. blackjack, cosh, sap
a piece of metal covered by leather with a flexible handle used for hitting people
3. black flag, pirate flag, Jolly Roger, blackjack
a flag usually bearing a white skull and crossbones on a black background indicates a pirate ship
4. 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
"blackjacks" in the verb sense
1. blackmail, blackjack, pressure
exert pressure on someone through threats
Source: WordNet® (An amazing lexical database of English)
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