Definitions of jack:

• noun:   male donkey
• noun:   any of several fast-swimming predacious fishes of tropical to warm-temperate seas
• noun:   tool for exerting pressure or lifting
• noun:   one of four face cards in a deck bearing a picture of a young prince
• noun:   small flag indicating a ship's nationality
• noun:   game equipment consisting of one of several small objects picked up while bouncing a ball in the game of jacks
• noun:   an electrical device consisting of a connector socket designed for the insertion of a plug
• noun:   a small worthless amount

  Example: "You don't know jack"

• noun:   immense East Indian fruit resembling breadfruit of; its seeds are commonly roasted
• noun:   someone who works with their hands; someone engaged in manual labor
• noun:   a man who serves as a sailor
• verb:   lift with a special device

  Example: "Jack up the car so you can change the tire"

• verb:   hunt with a jacklight
• name:  A male given name (very common: 1 in 317 males; popularity rank in the U.S.: #53)
• name:  A surname (common: 1 in 14285 families; popularity rank in the U.S.: #1852)
• name:  A female given name (rare: 1 in 100000 females; popularity rank in the U.S.: #3217)