I. -ˌjak noun
Date: 1591
1.
[ black + jack (vessel)]
: a tankard for beer or ale usually of tar-coated leather
2. : sphalerite
3. : a hand weapon typically consisting of a piece of leather-enclosed metal with a strap or springy shaft for a handle
4. : an often scrubby oak ( Quercus marilandica ) chiefly of the southeastern U.S. — called also blackjack oak
5. : a card game the object of which is to be dealt cards having a higher count than those of the dealer up to but not exceeding 21 — called also twenty-one, vingt-et-un
II. transitive verb
Date: 1905
1. : to strike with a blackjack
2. : to coerce with threats or pressure