Is “Slack” a Scrabble word?
Yes
SLACK
Valid in at least one Scrabble dictionary
Valid in these dictionaries
SOWPODS / CSW
Scrabble UK & International
TWL / NWL
Scrabble North America
Large English Dictionary
General English word list
Meaning of Slack
/slæk/
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”