[ jak ]
See synonyms for jack on Thesaurus.com
  1. any of various portable devices for raising or lifting heavy objects short heights, using various mechanical, pneumatic, or hydraulic methods.

  2. Also called knave. Cards. a playing card bearing the picture of a soldier or servant.

  1. Electricity. a connecting device in an electrical circuit designed for the insertion of a plug.

  2. Jack, Informal. fellow; buddy; man (usually used in addressing a stranger): Hey, Jack, which way to Jersey?

  3. Also called jackstone. Games.

    • one of a set of small metal objects having six prongs, used in the game of jacks.

    • one of any other set of objects, as pebbles, stones, etc., used in the game of jacks.

    • jacks, (used with a singular verb) a children's game in which small metal objects, stones, pebbles, or the like, are tossed, caught, and moved on the ground in a number of prescribed ways, usually while bouncing a rubber ball.

  4. any of several carangid fishes, especially of the genus Caranx, as C. hippos(crevalle jack, or jack crevalle ), of the western Atlantic Ocean.

  5. Slang. money: He won a lot of jack at the races.

  6. Slang: Vulgar. jack shit.

  7. Nautical.

    • a small flag flown at the jack staff of a ship, bearing a distinctive design usually symbolizing the nationality of the vessel.

    • Also called jack crosstree. either of a pair of crosstrees at the head of a topgallant mast, used to hold royal shrouds away from the mast.

  8. Jack, a sailor.

  9. a device for turning a spit.

  10. a small wooden rod in the mechanism of a harpsichord, spinet, or virginal that rises when the key is depressed and causes the attached plectrum to strike the string.

  11. Lawn Bowling. a small, usually white bowl or ball used as a mark for the bowlers to aim at.

  12. Also called clock jack. Horology. a mechanical figure that strikes a clock bell.

  13. a premigratory young male salmon.

  14. Theater. brace jack.

  15. Falconry. the male of a kestrel, hobby, or especially of a merlin.

verb (used with object)
  1. to lift or move (something) with or as if with a jack (usually followed by up): to jack a car up to change a flat tire.

  2. Informal. to increase, raise, or accelerate (prices, wages, speed, etc.) (usually followed by up).

  1. Informal. to boost the morale of; encourage (usually followed by up).

  2. Slang. to mess up, ruin, or injure (usually followed by up): The paint job was all jacked up.I jacked my shoulder when I fell.

  3. to jacklight.

verb (used without object)
  1. to jacklight.

  1. Carpentry. having a height or length less than that of most of the others in a structure; cripple: jack rafter; jack truss.

Verb Phrases
  1. jack off, Slang: Vulgar. to masturbate.

  2. jack up, Slang. to give oneself an injection of a controlled substance: After 30 heroin-free days, he was let out for the afternoon and came straight to my door, begging to jack up.

Idioms about jack

  1. every man jack, everyone without exception: They presented a formidable opposition, every man jack of them.

Origin of jack

First recorded in 1350–1400; Middle English jakke, Jakke used in addressing any male, especially a social inferior, variant of Jakken, variant of Jankin, equivalent to Jan “John” + -kin diminutive suffix; extended in sense to anything male, and as a designation for a variety of inanimate objects; see origin at John, -kin

Other definitions for jack (2 of 5)

[ jak ]

verb (used with object)Slang.
  1. to steal: Some neighborhood kids jacked her car and took it for a joyride.Hackers jacked my email account in a phishing scam.

  2. to rob: He got jacked on his way home from the club.

Origin of jack

First recorded in 1930–35; shortening of hijack

Other definitions for jack (3 of 5)

[ jak ]


Origin of jack

First recorded in 1605–15; from Portuguese jaca, from Malayalam cakka

Other definitions for jack (4 of 5)

[ jak ]

  1. a defensive coat, usually of leather, worn in medieval times by foot soldiers and others.

  2. a container for liquor, originally of waxed leather coated with tar.

Origin of jack

First recorded in 1325–75; Middle English jakke, from Middle French jaque(s), “short, plain upper garment,” probably after jacques “peasant” (see Jacquerie)

Other definitions for Jack (5 of 5)

[ jak ]

  1. a male given name, form of Jacob or John.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use jack in a sentence

British Dictionary definitions for jack (1 of 4)


/ (dʒæk) /

  1. a man or fellow

  2. a sailor

  1. the male of certain animals, esp of the ass or donkey

  2. a mechanical or hydraulic device for exerting a large force, esp to raise a heavy weight such as a motor vehicle

  3. any of several mechanical devices that replace manpower, such as a contrivance for rotating meat on a spit

  4. one of four playing cards in a pack, one for each suit, bearing the picture of a young prince; knave

  5. bowls a small usually white bowl at which the players aim with their own bowls

  6. electrical engineering a female socket with two or more terminals designed to receive a male plug (jack plug) that either makes or breaks the circuit or circuits

  7. a flag, esp a small flag flown at the bow of a ship indicating the ship's nationality: Compare Union Jack

  8. nautical either of a pair of crosstrees at the head of a topgallant mast used as standoffs for the royal shrouds

  9. a part of the action of a harpsichord, consisting of a fork-shaped device on the end of a pivoted lever on which a plectrum is mounted

  10. any of various tropical and subtropical carangid fishes, esp those of the genus Caranx, such as C. hippos (crevalle jack)

  11. Also called: jackstone one of the pieces used in the game of jacks

  12. US a slang word for money

  13. every man jack everyone without exception

  14. the jack Australian slang venereal disease

  1. jack of Australian slang tired or fed up with (something)

  1. to lift or push (an object) with a jack

  2. electrical engineering to connect (an electronic device) with another by means of a jack and a jack plug

  1. Also: jacklight US and Canadian to hunt (fish or game) by seeking them out or dazzling them with a flashlight

Origin of jack

C16 jakke, variant of Jankin, diminutive of John

British Dictionary definitions for jack (2 of 4)



/ (dʒæk) /

  1. short for jackfruit

Origin of jack

C17: from Portuguese jaca; see jackfruit

British Dictionary definitions for jack (3 of 4)


/ (dʒæk) /

  1. a short sleeveless coat of armour of the Middle Ages, consisting usually of a canvas base with metal plates

  2. archaic a drinking vessel, often of leather

Origin of jack

C14: from Old French jaque, of uncertain origin

British Dictionary definitions for Jack (4 of 4)


/ (dʒæk) /

  1. I'm all right, Jack British informal

    • a remark indicating smug and complacent selfishness

    • (as modifier): an ``I'm all right, Jack'' attitude

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with jack


In addition to the idioms beginning with jack

  • jack off
  • jack up

also see:

  • before you can say Jack Robinson

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.