Definition of "Slack" :
noun: a cord or rope or cable that is hanging loosely
"He took up the slack."
noun: the quality of being loose (not taut)
"He hadn't counted on the slackness of the rope."
noun: a soft wet area of low-lying land that sinks underfoot
noun: a stretch of water without current or movement
"Suddenly they were in a slack and the water was motionless."
noun: a noticeable deterioration in performance or quality
"A gradual slack in output."
noun: dust consisting of a mixture of small coal fragments and coal dust and dirt that sifts out when coal is passed over a sieve
verb: cause to heat and crumble by treatment with water
verb: become less in amount or intensity
verb: make less active or intense
verb: become slow or slower
verb: make less active or fast
"He slackened his pace as he got tired."
verb: release tension on
"Slack the rope."
verb: be inattentive to, or neglect
"He slacks his attention."
verb: avoid responsibilities and work, be idle
adjective: lacking in rigor or strictness
"Slack in maintaining discipline."
adjective: flowing with little speed as e.g. at the turning of the tide
adjective: not tense or taut
"Slack and wrinkled skin."