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