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See also: Slack and släck



  • IPA(key): /slæk/
  • (file)
  • Rhymes: -æk

Etymology 1[edit]

From Middle English slak, from Old English slæc (slack), from Proto-Germanic *slakaz. For sense of coal dust, compare slag.


slack (countable and uncountable, plural slacks)

  1. (uncountable) The part of anything that hangs loose, having no strain upon it.
    the slack of a rope or of a sail
    take in the slack
  2. (countable) A tidal marsh or shallow that periodically fills and drains.
  3. (uncountable, psychotherapy) Unconditional listening attention given by client to patient.
    • 1979, Richard Dean Rosen, Psychobabble, page 93:
      The counselor is directed to give his client "free attention," or "slack," performing a kind of vigil, a version of Carl Rogers's "unconditional positive regard."
    • 1983, Harvey Jackins, The Reclaiming of Power, page 14:
      We have apparently been doing this all our lives, since we were first distressed. This collection of ancient habits seems to be "energized" by the presence, or even the promise, of "slack" or free attention from any person in the situation []
  4. Attributive form of slacks (semi-formal trousers).
    • 1943, Jacob Armstrong Swisher, Iowa in Times of War, State Historical Society of Iowa, page 124:
      The breeches formerly worn with those spiral leggings have been succeeded by full length, slack-type trousers which are loose at the knee and around the calf.
    • 1970, Harry A. Cobrin, The Men’s Clothing Industry: Colonial Through Modern Times, New York, N.Y.: Fairchild Publications, Inc., →ISBN, page 7:
      Recently though, slack manufacturers have been cuddling under the wings of the clothing industry to a greater extent than ever, for it has become good business to promote separate slacks and sport coats as a coordinated sales unit.
    • 2004, Pei Pin Han, “Friendship for 54 Years”, in Amy Lanping Sung, Hu Kung-Chung Chien, editors, Shu Chien: Tributes on His 70th Birthday, World Scientific, →ISBN, page 38:
      At that time, it was customary for male college students in Peking to wear long gowns. With a pair of slacks and leather shoes, plus a scarf in the winter, Shu looked very handsome. I tried to wear the gown for two days, and gave it up because I found it difficult to reach the slack pockets under it.
Derived terms[edit]


slack (comparative slacker, superlative slackest)

  1. (normally said of a rope) Lax; not tense; not firmly extended.
    a slack rope
  2. Weak; not holding fast.
    a slack hand
  3. Moderate in some capacity.
    1. Moderately warm.
      a slack oven
    2. Moderate in speed.
      a slack wind
  4. Lacking diligence or care; not earnest or eager.
    slack in duty or service
  5. Not active or busy, successful, or violent.
    Business is slack.
    • 1928, Lawrence R. Bourne, chapter 3, in Well Tackled![1]:
      “They know our boats will stand up to their work,” said Willison, “and that counts for a good deal. A low estimate from us doesn't mean scamped work, but just for that we want to keep the yard busy over a slack time.”
    • 1940 December, “Notes and News: Waterloo & City Tube Modernisation”, in Railway Magazine, page 668:
      In the slack hours the service is maintained by single motor-coaches.
  6. Excess; surplus to requirements.
    the slack capacity of an oil pipeline
  7. (slang, Caribbean, Jamaica) Vulgar; sexually explicit, especially in dancehall music.
  8. (linguistics) Lax.
Derived terms[edit]


slack (not comparable)

  1. Slackly.
    slack dried hops

Etymology 2[edit]

From Middle English slakken, slaken, from Old English slacian, from Proto-Germanic *slakōną (to slack, slacken).


slack (third-person singular simple present slacks, present participle slacking, simple past and past participle slacked)

  1. (transitive, intransitive) To slacken.
    • c. 1590 (date written), [John Lyly], Mother Bombie. [], 2nd edition, London: [] Thomas Creede, for Cuthbert Burby, published 1598, →OCLC, Act II, scene ii:
      I maruell I heare no nevves of Dromio, either hee ſlackes the matter, or betraies his Maiſter, I dare not motion anie thing to Stellio, till I knovv vvhat my boy hath don, Ile hunt him out, if the loiterſacke be gone ſpringing into a Tauerne, Ile fetch him reeling out.
    • 1692–1717, Robert South, Twelve Sermons Preached upon Several Occasions, 6th edition, volumes (please specify |volume=I to VI), London: [] J[ames] Bettenham, for Jonah Bowyer, [], published 1727, →OCLC:
      In this business of growing rich, poor men [] should slack their pace.
  2. (obsolete) To mitigate; to reduce the strength of.
  3. To lose cohesion or solidity by a chemical combination with water; to slake.
    Lime slacks.
Derived terms[edit]

Etymology 3[edit]

Either from the adjective in Etymology 1 or the verb in Etymology 2.


slack (plural slacks)

  1. (rail transport) A temporary speed restriction where track maintenance or engineering work is being carried out at a particular place.
    • 1939 June, “Pertinent Paragraphs: Pitfalls”, in Railway Magazine, page 456:
      This pitfall, beginning in February and finishing in May, resulted in a drop of about 3 ft. in the platform level; during this period it was necessary to level the track three times weekly, and impose a service slack of 15 m.p.h. The subsidence appears now to have finished, and normal speed is once again permitted.
    • 1949 September and October, “The "Nord Express"”, in Railway Magazine, page 336:
      The train runs slowly with frequent slacks for bridge and culvert repairs. At one point occurs the changeover from left- to right-hand running.
    • 1960 February, R. C. Riley, “The London-Birmingham services - Past, Present and Future”, in Trains Illustrated, page 103:
      A 40 m.p.h. slack at West Ruislip, quickly followed by a 30 m.p.h. slack at Gerrards Cross, increased our lateness to four minutes at High Wycombe.

Etymology 4[edit]

From Middle English slak, from Old Norse slakki (a slope). Cognate with Icelandic slakki, Norwegian slakke.


slack (plural slacks)

  1. (countable) A valley, or small, shallow dell.

Etymology 5[edit]

Probably from German Schlacke (dross, slag). Doublet of slag.


slack (uncountable)

  1. (mining) Small coal; coal dust.
    Synonym: culm
    • 1905, Colliery Engineer, volume 25, page 107:
      One of the important improvements of recent years has been attained by mixing the peat pulp as it passes through the grinding machine, with other inflammable materials, such as bituminous coal dust, or slack []
    • 1959 April, P. Ransome-Wallis, “The Southern in Trouble on the Kent Coast”, in Trains Illustrated, London: Ian Allan Publishing, →ISSN, →OCLC, page 220:
      It had rather a woolly and uneven beat and was inclined to prime, but there was no trouble with steaming even though the tender contained mostly small slack and dust.
Derived terms[edit]