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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 []
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. To slacken.
    • 1692–1717, Robert South, Twelve Sermons Preached upon Several Occasions, volume (please specify |volume=I to VI), 6th edition, London: [] J[ames] Bettenham, for Jonah Bowyer, [], published 1727, OCLC 21766567:
      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.
    • 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.
    • 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 0141-9935, OCLC 35845948, 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]