black ‧ jack /ˈblækdʒæk/ BrE AmE noun
[ Sense 1: Date: 1900-2000 ; Origin: black + ⇨ ↑ jack 1 (2) ]
[ Sense 2: Date: 1800-1900 ; Origin: black + jack 'tool' (16-20 centuries) ]
1 . [uncountable] a card game, usually played for money, in which you try to get as close to 21 points as possible
2 . [countable] a weapon like a stick covered with leather, used to hit people