slack \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. s.rj to let loose,
   to throw. cf. slake.
   lax; not tense; not hard drawn; not firmly extended; as, a
   slack rope.
   1913 webster

   2. weak; not holding fast; as, a slack hand. --milton.
      1913 webster

   3. remiss; backward; not using due diligence or care; not
      earnest or eager; as, slack in duty or service.
      1913 webster

            the lord is not slack concerning his promise, as
            some men count slackness.             --2 pet. iii.
                                                  9.
      1913 webster

   4. not violent, rapid, or pressing; slow; moderate; easy; as,
      business is slack. "with slack pace." --chaucer.
      1913 webster

            c?sar . . . about sunset, hoisting sail with a slack
            southwest, at midnight was becalmed.  --milton.
      1913 webster

   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.
      1913 webster

   syn: loose; relaxed; weak; remiss; backward; abated;
        diminished; inactive; slow; tardy; dull.
        1913 webster
see also:
slacker slackest slake slack in stays slack water slack-water navigation