blackjack in WordNet English dictionary

1. a flag usually bearing a white skull and crossbones on a black background; indicates a pirate ship
   black flag  pirate flag  Jolly Roger  blackjack 
   
2. 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
   blackjack  twenty-one  vingt-et-un 
   
3. a piece of metal covered by leather with a flexible handle; used for hitting people
   blackjack  cosh  sap 
   
4. 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
   blackjack oak  blackjack  jack oak  Quercus marilandica 
   

1. exert pressure on someone through threats
   blackmail  blackjack  pressure