\ˈslak \

Definition of slack 

(Entry 1 of 5)

1 : not using due diligence, care, or dispatch : negligent

2a : characterized by slowness, sluggishness, or lack of energy a slack pace

b : moderate in some quality especially : moderately warm a slack oven

c : blowing or flowing at low speed the tide was slack

3a : not tight or taut a slack rope

b : lacking in usual or normal firmness and steadiness : weak slack muscles slack supervision

4 : wanting in activity : dull a slack market

5 : lacking in completeness, finish, or perfection a very slack piece of work


slacked; slacking; slacks

Definition of slack (Entry 2 of 5)

intransitive verb

1 : to be or become slack

2 : to shirk or evade work or duty

transitive verb

1a : to be slack or negligent in performing or doing

b : lessen, moderate

2 : to release tension on : loosen

3a : to cause to abate

b : slake sense 3


noun (1)

Definition of slack (Entry 3 of 5)

1 : cessation in movement or flow

2 : a part of something that hangs loose without strain take up the slack of a rope

3 : trousers especially for casual wear usually used in plural

4 : a dull season or period

5a : a part that is available but not used some slack in the budget

b : a portion (as of labor or resources) that is required but lacking hired a temp to take up the slack

6 : additional leeway or relief from pressure usually used with cut refused to cut me some slack on the schedule


noun (2)

Definition of slack (Entry 4 of 5)

dialectal, England

: a pass between hills


noun (3)

Definition of slack (Entry 5 of 5)

: the finest screenings of coal produced at a mine unusable as fuel unless cleaned

Keep scrolling for more

Other Words from slack


slackly adverb
slackness noun

Synonyms & Antonyms for slack

Synonyms: Adjective

careless, derelict, disregardful, lax, lazy, neglectful, neglecting, negligent, remiss

Synonyms: Verb

ease, loosen, relax, slacken

Antonyms: Adjective

attentive, careful, conscientious, nonnegligent

Antonyms: Verb

strain, stretch, tense, tension, tighten

Visit the Thesaurus for More 

Choose the Right Synonym for slack


negligent, neglectful, lax, slack, remiss mean culpably careless or indicative of such carelessness. negligent implies inattention to one's duty or business. negligent about writing a note of thanks neglectful adds a more disapproving implication of laziness or deliberate inattention. a society callously neglectful of the poor lax implies a blameworthy lack of strictness, severity, or precision. a reporter lax about accurate quotation slack implies want of due or necessary diligence or care. slack workmanship remiss implies blameworthy carelessness shown in slackness, forgetfulness, or neglect. had been remiss in their familial duties

Examples of slack in a Sentence


His broken arm hung slack at his side. The rope suddenly went slack. He accused the government of slack supervision of nuclear technology.


They need to stop slacking and get down to work. the skipper ordered the crew to slack off the sheets on the mainsail
See More

First Known Use of slack


before the 12th century, in the meaning defined at sense 1


13th century, in the meaning defined at intransitive sense 1

Noun (1)

1756, in the meaning defined at sense 1

Noun (2)

14th century, in the meaning defined above

Noun (3)

1729, in the meaning defined above

History and Etymology for slack


Middle English slak, from Old English sleac; akin to Old High German slah slack, Latin laxus slack, loose, languēre to languish, Greek lagnos lustful and perhaps to Greek lēgein to stop

Noun (2)

Middle English slak, from Old Norse slakki

Noun (3)

earlier sleck, probably from Middle Dutch slacke, slecke slag

Keep scrolling for more

Learn More about slack

Statistics for slack

Look-up Popularity

Time Traveler for slack

The first known use of slack was before the 12th century

See more words from the same century

Keep scrolling for more

More Definitions for slack



English Language Learners Definition of slack

 (Entry 1 of 2)

: not stretched or held in a tight position

: not busy : lacking the expected or desired activity

: doing something poorly because you are not putting enough care or effort into it



English Language Learners Definition of slack (Entry 2 of 2)

: to give little or no effort or attention to work


\ˈslak \

Kids Definition of slack

 (Entry 1 of 3)

1 : careless sense 1, negligent They were slack in all things, without order or discipline.— Jack London, The Call of the Wild

2 : not energetic : slow a slack pace

3 : not tight or firm a slack rope a slack jaw

4 : not busy or active Business is slack.


slacked; slacking

Kids Definition of slack (Entry 2 of 3)

1 : to make or become looser, slower, or less energetic

2 : to avoid work

Other Words from slack

slacker \ˈsla-​kər \ noun



Kids Definition of slack (Entry 3 of 3)

1 : a part (as of a rope or sail) that hangs loose without strain

2 slacks plural : dressy pants

3 : a portion (as of work or resources) that is required but lacking He was hired to take up the slack.

4 : additional relief from pressure

Hint: This sense is usually used with cut.
  • Can you cut me some slack on the schedule?

Keep scrolling for more

More from Merriam-Webster on slack

Rhyming Dictionary: Words that rhyme with slack

Thesaurus: All synonyms and antonyms for slack

Spanish Central: Translation of slack

Nglish: Translation of slack for Spanish Speakers

Britannica English: Translation of slack for Arabic Speakers

Comments on slack

What made you want to look up slack? Please tell us where you read or heard it (including the quote, if possible).


having a pattern of small flowers

Get Word of the Day daily email!

Test Your Vocabulary

Find the Cousins

  • a-large-tree-with-many-branches
  • Which pair shares a common word ancestor?
True or False

Test your knowledge - and maybe learn something along the way.

Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!