Noun

Singular jack

Plural jacks

jack (plural jacks)

1. A mechanical device used to raise and (temporarily) support a heavy object.

   She used a jack to lift her car and changed the tire.

2. A man or men in general.
   • Every man jack.
3. A male animal.
4. (card games) The card ranking between the ten and queen of any suit, picturing a knave or prince on its face, and in some card games having a value of eleven.
5. (zoology) A male ass.
6. A surface-mounted connector for electrical, especially telecommunications, equipment.

   telephone jack

7. (sports) A target ball in bowls, etc; a jack-ball.
8. (games) A small, six-pointed playing piece used in the game of jacks.
9. (colloquial) Nothing, jackshit.

   You haven't done jack. Get up and get this room cleaned up right now!

10. (nautical) A small flag at the bow of a ship.
11. (nautical) A naval ensign flag flown from the main mast, mizzen mast, or the aft-most major mast of (especially) British sailing warships; Union Jack.
12. (military) A coarse and cheap medieval coat of defense, especially one made of leather.
    • 1786, Francis Grose, A Treatise on Ancient Armour and Weapons, page 15:

      The aketon, gambeson, vambasium, and jack were military vestments, calculated for the defence of the body, differing little from each other, except in their names, their materials and construction were nearly the same, the authorities quoted in the notes, shew they were all composed of many folds of linen, stuffed with cotton, wool or hair, quilted, and commonly covered with leather, made of buck or doe skin.

13. (two-up) A penny with a head on both sides, used for cheating. (Reference: Sidney J. Baker, The Australian Language, second edition, 1966, chapter XI section 3, page 243.)
14. (slang) Money.
15. (slang, Appalachians) A smooth often ovoid large gravel or small cobble in a natural water course.
16. A common name for the freshwater pike, green pike or pickerel.
17. Large California rockfish.
18. An order of marine fish in the Carangidae family.
19. (obsolete, nautical) A sailor; a "jack tar".

Synonyms

• (playing card): knave
• (male ass): jackass

Derived terms

• bootjack
• jack of all trades
• jack plug
• Union Jack
• bicolor jack
• blackfin jack
• cheap-jack
• cottonmouth jack

• Crevalle jack
• green jack
• horse-eye jack
• jack over
• jack rabbit
• one-eyed jack
• Senegal jack
• whitetongue jack
• yellowfin jack

Jack may refer to:

• Jack (hero), an archetypal English hero.
• Jack (CAD software), a 3-D ergonomics and human factors CAD package
• JACK Intelligent Agents, a multi-agent platform written in Java
• Jack (connector), an electrical connector
• JACK Audio Connection Kit, a computer sound server
• Jack (device), a device used to lift heavy objects
• Jack (fish), several species of fish
• Jack (donkey), a male donkey
• Jack (human modeling), a human modeling and simulation system
• Jack (playing card), the lowest face card in a deck of playing cards
• Jack (software), an audio CD ripper
• Jack (tree) (Mangifera caesia), a relative of the mango
• The Incredible Jack, an integrated software product of the 1980s[1]
• A target ball in bowls, etc.
• Jacks, maritime flags flown from the bow of a ship
• Jack or Jack Tar, a sailor
• Jack, the name of one of the Clayton Windmills, a pair of windmills at Clayton, Sussex
• Jack (band), a British independent pop group signed to the Too Pure label
• Jack (film), a 1996 film starring Robin Williams
• Jack (2004 film), a 2004 film starring Anton Yelchin and Stockard Channing
• Jack (webcomic), an anthropomorphic webcomic
• Roasting jack, a device for turning a spit
• Jack, an archaic unit of volume equal to two fluid ounces
• Monterey Jack, a variety of cheese