Slow in movement; tardy.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.Slow in action; lacking in promptness or diligence; negligent; remiss.Not tight; not tense or taut; relaxed; loose: as, a slack rope; slack rigging; a slack rein; figuratively, languid; limp; feeble; weak.Not compacted or firm; loose.Lacking in briskness or activity; dull: said especially of business.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.Synonyms Careless, dilatory, tardy, inactive.n. 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.n. A remission; an interval of rest, inactivity, or dullness, as in trade or work; a slack period.n. A slack-water haul of the net: as, two or three slacks are taken daily.n. A long pool in a streamy river.In a slack manner; slowly; partially; insufficiently: as, slack dried hops; bread slack baked.To become slack or slow; slacken; become slower: as, a current of water slacks.To become less tense, firm, or rigid; decrease in tension.To abate; become less violent.To become languid; languish; fail; flag.To make slack or slow; retard.To make slack or less tense; loosen; relax: as, to slack a rope or a bandage.To relax; let go the hold of; lose or let slip.To make less intense, violent, severe, rapid, etc.; abate; moderate; diminish; hence, to mitigate; relieve.To be remiss in or neglectful of; neglect.To make remiss or neglectful.To slake (lime). See slake, transitive verb, 3.To cool in water.To retard the speed of, as a railway-train.n. The finer screenings of coal; coal-dirt; especially, the dirt of bituminous coal.n. A sloping hillside.n. An opening between hills; a hollow where no water runs.n. A common.n. A morass.n. 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.n. plural A sailor's loose trousers.n. Feeble, foolish talk.