Definition of jack:
a mechanical device
used to raise
and (temporarily) support a heavy object; (playing cards
) The card ranking between the ten
of any suit, with a picture of a knave or prince on its face; often with value 11
to use a jack; (slang) To hit the ball hard
"he jacked the car up so that he could replace the brake pads."
(slang) A player has hit a home run
"jack! Tie score."