slack (adj.)

Old English slæc "remiss, lax, characterized by lack of energy, sluggish, indolent, languid; slow, gentle, easy," from Proto-Germanic *slakas (source also of Old Saxon slak, Old Norse slakr, Old High German slah "slack," Middle Dutch lac "fault, lack"), from PIE root *sleg- "be slack, be languid."

Sense of "not tight" (in reference to things) is first recorded c. 1300. As an adverb from late 14c. Slack-key (1975) translates Hawaiian ki ho'alu. Slack water (n.) "time when tide is not flowing" is from 1769. Slack-handed "remiss" is from 1670s. Slack-baked "baked imperfectly, half-baked" is from 1823; figuratively from 1840.

slack (n.1)

early 14c., "cessation" (of pain, grief, etc.), from slack (adj.). Meaning "a cessation of flow in a current or tide" is from 1756; that of "still stretch of a river" is from 1825. Meaning "loose part or end" (of a rope, sail, etc.) is from 1794; hence figurative senses in take up the slack (1930 figuratively) and slang cut (someone) some slack (1968). Meaning "quiet period, lull" is from 1851. Slacks "loose trousers" first recorded 1824, originally military.

slack (n.2)

"coal dust," mid-15c., sleck, of uncertain origin, probably related to Middle Dutch slacke, Middle Low German slecke "slag, small pieces left after coal is screened," perhaps related to slagge "splinter flying off metal when it is struck" (see slag (n.)).

slack (v.)

1510s, "to moderate, make slack," back-formed from slack (adj.) after the original verb veered into the specialized sense of slake. Meaning "be remiss, inactive or idle, fail to exert oneself" is attested from 1540s; current use is probably a re-coining from c. 1904 (see slacker, and compare Old English slacful "lazy," sleacmodnes "laziness"). Related: Slacked; slacking.

Definitions of slack
slack (v.)
avoid responsibilities and work, be idle;
slack (v.)
be inattentive to, or neglect;
He slacks his attention
slack (v.)
release tension on;
slack the rope
slack (v.)
make less active or fast;
Synonyms: slacken / slack up / relax
slack (v.)
become slow or slower;
Synonyms: slow / slow down / slow up / slacken
slack (v.)
make less active or intense;
Synonyms: slake / abate
slack (v.)
become less in amount or intensity;
Synonyms: abate / let up / slack off / die away
slack (v.)
cause to heat and crumble by treatment with water;
slack lime
Synonyms: slake
slack (n.)
dust consisting of a mixture of small coal fragments and coal dust and dirt that sifts out when coal is passed over a sieve;
slack (n.)
a noticeable deterioration in performance or quality;
a gradual slack in output
Synonyms: slump / drop-off / falloff / falling off
slack (n.)
a stretch of water without current or movement;
suddenly they were in a slack and the water was motionless
Synonyms: slack water
slack (n.)
a soft wet area of low-lying land that sinks underfoot;
Synonyms: mire / quagmire / quag / morass
slack (n.)
the quality of being loose (not taut);
Synonyms: slackness
slack (n.)
a cord or rope or cable that is hanging loosely;
he took up the slack
slack (adj.)
not tense or taut;
slack sails
a slack rope
slack and wrinkled skin
a slack grip
Synonyms: loose
slack (adj.)
flowing with little speed as e.g. at the turning of the tide;
slack water
slack (adj.)
lacking in rigor or strictness;
slack in maintaining discipline
Synonyms: lax