Slack, a. [Compar.Slacker (?); superl.Slackest.] [OE. slak, AS. sleac; akin to OS. slak, OHG. slah, Prov. G. schlack, Icel. slakr, Sw. slak; cf. Skr. sṛj to let loose, to throw. Cf. Slake.] Lax; not tense; not hard drawn; not firmly extended; as, a slack rope.
2. Weak; not holding fast; as, a slack hand. Milton.
3. Remiss; backward; not using due diligence or care; not earnest or eager; as, slack in duty or service.
The Lord is not slack concerning his promise, as some men count slackness. 2 Pet. iii. 9.
4. Not violent, rapid, or pressing; slow; moderate; easy; as, business is slack. “With slack pace.” Chaucer.
C�sar... about sunset, hoisting sail with a slack southwest, at midnight was becalmed. Milton.
Slack in stays(Naut.), slow in going about, as a ship. — Slack water, the time when the tide runs slowly, or the water is at rest; or the interval between the flux and reflux of the tide. — Slack-water navigation, navigation in a stream the depth of which has been increased, and the current diminished, by a dam or dams.
Syn. — Loose; relaxed; weak; remiss; backward; abated; diminished; inactive; slow; tardy; dull.