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. In some card games has a value of eleven based on its rank, but in many card games has a value of ten like the ten, queen, and king cards. Also called a knave.
5. (archaic) A knave (a servant or later, a deceitful man).
   • 1799, THE SCOTS MAGAZINE OR GENERAL REPOSITORY OF LITERATURE, HISTORY, AND POLITICS, page 171:

     Fly may signify a winged insect, or part of a Jack. Jack itself is sometimes a roaster of meat, and at others a contraction of John, a knave, a Japan mug, or an instrument to draw off boots.

6. (zoology) A male ass.
7. A surface-mounted connector for electrical, especially telecommunications, equipment.

   telephone jack

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

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

11. (nautical) A small flag at the bow of a ship.
12. (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.
13. (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.

14. (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.)
15. (slang) Money.
16. (slang, Appalachians) A smooth often ovoid large gravel or small cobble in a natural water course.
17. A common name for the freshwater pike, green pike or pickerel.
18. Large California rockfish.
19. An order of marine fish in the Carangidae family.
20. (obsolete, nautical) A sailor; a "jack tar".

Synonyms

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

Derived terms

• bicolor jack
• blackfin jack
• bootjack
• cheap-jack
• cottonmouth jack
• Crevalle jack
• green jack
• horse-eye jack
• jack-o'-lantern

• jack of all trades
• jack over
• jack plug
• jack rabbit
• one-eyed jack
• Senegal jack
• whitetongue jack
• Union Jack
• yellowfin jack

Jack