1. moving slowly; sluggish: a slack pace.
2. lacking in activity; not busy: a slack season for the travel business.
3. not tense or taut; loose: a slack rope; slack muscles. see synonyms at loose.
4. lacking firmness; flaccid: a slack grip.
5. lacking in diligence or due care or concern; negligent: a slack worker. see synonyms at negligent.
6. flowing or blowing with little speed: a slack current; slack winds.
7. linguistics pronounced with the muscles of the tongue and jaw relatively relaxed; lax.
8. to make slower or looser; slacken.
9. to be careless or remiss in doing: slack one's duty.
10. to slake (lime).
11. to be or become slack.
12. to evade work; shirk.
13. A loose part, as of a rope or sail.
14. A lack of tension; looseness.
15. A period of little activity; a lull.
16. A cessation of movement in a current of air or water.
17. an area of still water.
18. unused capacity: still some slack in the economy.
19. casual trousers that are not part of a suit.
20. in a slack manner: a banner hanging slack.
21. slack off to decrease in activity or intensity.
22. cut slang to make an allowance for (someone), as in allowing more time to finish something.
23. A mixture of coal fragments, coal dust, and dirt that remains after screening coal.
24. chiefly british A small dell or hollow.
25. chiefly british A bog; a morass.

1. small coal; coal dust.
2. A valley, or small, shallow dell.
3. the part of anything that hangs loose, having no strain upon it.
4. A tidal marsh or shallow, that periodically fills and drains.
5. lax; not tense; not hard drawn; not firmly extended.
6. weak; not holding fast.
7. remiss; backward; not using due diligence or care; not earnest or eager.
8. not violent, rapid, or pressing.
9. slackly.
10. to mitigate; to reduce the strength of.
11. to procrastinate; to be lazy
12. to refuse or dislike exerting effort

1. lax; not tense; not hard drawn; not firmly extended.
2. weak; not holding fast.
3. remiss; backward; not using due diligence or care; not earnest or eager.
4. not violent, rapid, or pressing; slow; moderate; easy.
5. slackly.
6. small coal; also, coal dust; culm.
7. A valley, or small, shallow dell.
8. the part of anything that hangs loose, having no strain upon it.
9. to become slack; to be made less tense, firm, or rigid; to decrease in tension.
10. to be remiss or backward; to be negligent.
11. to lose cohesion or solidity by a chemical combination with water; to slake.
12. to abate; to become less violent.
13. to lose rapidity; to become more slow.
14. to languish; to fail; to flag.
15. to end; to cease; to desist; to slake.
16. to render slack; to make less tense or firm.
17. to neglect; to be remiss in.
18. to deprive of cohesion by combining chemically with water; to slake.
19. to cause to become less eager; to repress; to make slow or less rapid; to retard.
20. to cause to become less intense; to mitigate; to abate; to ease.

1. slow in movement; tardy.
2. slow in flow; sluggish or at rest: as, slack water: specifically noting the tide, or the time when the tide is at rest—that is, between the flux and reflux.
3. slow in action; lacking in promptness or diligence; negligent; remiss.
4. not tight; not tense or taut; relaxed; loose: as, a slack rope; slack rigging; a slack rein; figuratively, languid; limp; feeble; weak.
5. not compacted or firm; loose.
6. lacking in briskness or activity; dull: said especially of business.
7. in hydraulic engineering, a pool or pond behind a dam serving for needs of navigation. such ponds are used with a series of dams and locks, to render small streams navigable.
8.
9. the part of a rope or the like that hangs loose, having no stress upon it; also, looseness, as of the parts of a machine.
10. A remission; an interval of rest, inactivity, or dullness, as in trade or work; a slack period.
11. A slack-water haul of the net: as, two or three slacks are taken daily.
12. A long pool in a streamy river.
13. in a slack manner; slowly; partially; insufficiently: as, slack dried hops; bread slack baked.
14. to become slack or slow; slacken; become slower: as, a current of water slacks.
15. to become less tense, firm, or rigid; decrease in tension.
16. to abate; become less violent.
17. to become languid; languish; fail; flag.
18. to make slack or slow; retard.
19. to make slack or less tense; loosen; relax: as, to slack a rope or a bandage.
20. to relax; let go the hold of; lose or let slip.
21. to make less intense, violent, severe, rapid, etc.; abate; moderate; diminish; hence, to mitigate; relieve.
22. to be remiss in or neglectful of; neglect.
23. to make remiss or neglectful.
24. to slake (lime). see slake, transitive verb, 3.
25. to cool in water.
26. to retard the speed of, as a railway-train.
27. the finer screenings of coal; coal-dirt; especially, the dirt of bituminous coal.
28. A sloping hillside.
29. an opening between hills; a hollow where no water runs.
30. A common.
31. A morass.
32. the interval of slack water, when the tide is at rest, either at high or low tide; sluggishness of the current, at that time see slack, adjective, 2.
33. plural A sailor's loose trousers.
34. feeble, foolish talk.

1. be inattentive to, or neglect
2. cause to heat and crumble by treatment with water
3. become slow or slower
4. make less active or intense
5. not tense or taut
6. release tension on
7. dust consisting of a mixture of small coal fragments and coal dust and dirt that sifts out when coal is passed over a sieve
8. a soft wet area of low-lying land that sinks underfoot
9. flowing with little speed as e.g. at the turning of the tide
10. the quality of being loose (not taut)
11. make less active or fast
12. lacking in rigor or strictness
13. avoid responsibilities and work, be idle
14. a cord or rope or cable that is hanging loosely
15. become less in amount or intensity
16. a noticeable deterioration in performance or quality
17. a stretch of water without current or movement