1. dust consisting of a mixture of small coal fragments and coal dust and dirt that sifts out when coal is passed over a sieve

2. a noticeable deterioration in performance or quality;

"the team went into a slump"

"a gradual slack in output"

"a drop-off in attendance"

"a falloff in quality"

3. a stretch of water without current or movement;

"suddenly they were in slack water"

4. the condition of being loose (not taut);

"he hadn't counted on the slackness of the rope"

5. a cord or rope or cable that is hanging loosely;

"he took up the slack"

1. avoid responsibilities and work, be idle

2. be inattentive to, or neglect;

"He slacks his attention"

3. release tension on;

"slack the rope"

4. make less active or fast;

"He slackened his pace as he got tired"

"Don't relax your efforts now"

5. become slow or slower;

"Production slowed"

6. make less active or intense

7. become less in amount or intensity;

"The storm abated"

"The rain let up after a few hours"

8. cause to heat and crumble by treatment with water;

"slack lime"

1. not tense or taut;

"the old man's skin hung loose and gray"

"slack and wrinkled skin"

"slack sails"

"a slack rope"

2. lacking in strength or firmness or resilience;

"flaccid muscles"

"took his lax hand in hers"

"gave a limp handshake"

"a limp gesture as if waving away all desire to know" G.K.Chesterton

"a slack grip"

3. flowing with little speed as e.g. at the turning of the tide;

"slack water"

4. lacking in rigor or strictness;

"such lax and slipshod ways are no longer acceptable"

"lax in attending classes"

"slack in maintaining discipline"