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noun \ˈjak\

Simple Definition of jack

  • : a device used for lifting something heavy (such as a car)

  • : a playing card that has a picture of a soldier or servant and that is worth more than a ten and less than a queen

  • : a small opening where something connects with a wire to something else

Source: Merriam-Webster's Learner's Dictionary

Full Definition of jack

  1. 1 a :  man —usually used as an intensive in such phrases as every man jack b often capitalized :  sailor c (1) :  servant, laborer (2) :  lumberjack

  2. 2 :  any of various usually mechanical devices: as a :  a device for turning a spit b :  a usually portable mechanism or device for exerting pressure or lifting a heavy body a short distance

  3. 3 :  something that supports or holds in position: as a :  an iron bar at a topgallant masthead to support a royal mast and spread the royal shrouds b :  a wooden brace fastened behind a scenic unit in a stage set to prop it up

  4. 4 a :  any of several fishes; especially :  any of various carangids b :  a male donkey c :  jackrabbit d :  any of several birds (as a jackdaw)

  5. 5 a :  a small white target ball in lawn bowling b :  a small national flag flown by a ship c (1) plural but sing in constr :  a game played with a set of small objects that are tossed, caught, and moved in various figures (2) :  a small 6-pointed metal object used in the game of jacks

  6. 6 a :  a playing card carrying the figure of a soldier or servant and ranking usually below the queen b :  jackpot 1a(2)

  7. 7 slang :  money

  8. 8 :  a female fitting in an electric circuit used with a plug to make a connection with another circuit

  9. 9 a :  applejack b :  brandy

  10. 10 :  jackknife 2

  11. 11 :  monterey jack

Examples of jack in a sentence

  1. <I'd buy that watch, but I don't have the jack right now.>

  2. <a Portuguese ship flying the national jack>

Origin of jack

Middle English Jacke, familiar term of address to a social inferior, nickname for Johan John

First Known Use: 1548




Definition of jack

  1. intransitive verb
  2. :  to hunt or fish at night with a jacklight

  3. transitive verb
  4. 1 :  to hunt or fish for at night with a jacklight

  5. 2 a :  to move or lift by or as if by a jack b :  to raise the level of —usually used with up <jack up the price> c :  to take to task

jacker noun

Circa 1841

First Known Use of jack

circa 1841

JACK Defined for Kids



noun \ˈjak\

Definition of jack for Students

  1. 1 :  a device for lifting something heavy a short distance

  2. 2 :  a playing card with the picture of a young man

  3. 3 :  a small six-pointed usually metal object used in a children's game (jacks)

  4. 4 :  a socket used with a plug to connect one electric circuit with another




Definition of jack for Students


  1. :  to move or lift with a special device <We need to jack up the car.>

Seen and Heard

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