noun

1. The part of anything that hangs loose, having no strain upon it.

   “take in the slack”

2. A tidal marsh or shallow that periodically fills and drains.

Synonyms: culm, slough

adjective

1. (normally said of a rope) Lax; not tense; not firmly extended.

   “a slack rope”

2. Weak; not holding fast.

   “a slack hand”

3. Lacking diligence or care; not earnest or eager.

   “slack in duty or service”

Synonyms: easy, moderate, slow

adverb

1. Slackly.

   “slack dried hops”