slack¹ / slak/ • adj. 1. not taut or held tightly in position; loose: a slack rope her mouth went slack.2. (of business) characterized by a lack of work or activity; quiet: business was rather slack. ∎  slow or sluggish: they were working at a slack pace. ∎  having or showing laziness or negligence: slack accounting procedures.3. (of a tide) neither ebbing nor flowing: soon the water will become slack, and the tide will turn.• n. 1. the part of a rope or line that is not held taut; the loose or unused part: I picked up the rod and wound in the slack.2. (slacks) casual trousers.3. inf. a spell of inactivity or laziness: he slept deeply, refreshed by a little slack in the daily routine.• v. [tr.] 1. loosen (something, esp. a rope). ∎  reduce the intensity or speed of (something); slacken: the horse slacked his pace. ∎  [intr.] (slack off) decrease in quantity or intensity: the flow of blood slacked off. ∎  [intr.] inf. work slowly or lazily: she reprimanded her girls if they were slacking. ∎  [intr.] (slack up) slow down: the animal doesn't slack up until he reaches the trees.2. slake (lime).• adv. loosely: their heads were hanging slack in attitudes of despair.PHRASES: cut someone some slack inf. allow someone some leeway in their conduct.take (or pick) up the slack1. use up a surplus or improve the use of resources to avoid an undesirable lull in business: as domestic demand starts to flag, foreign demand will help pick up the slack.2. pull on the loose end or part of a rope in order to make it taut.DERIVATIVES: slack·ly adv.slack·ness n.slack² • n. coal dust or small pieces of coal.