not taut or held tightly in position; loose

a slack rope

her mouth went slack

(of business or trade) characterized by a lack of work or activity; quiet

business was rather slack

having or showing laziness or negligence

slack accounting procedures

lewd

the veteran king of slack chat

(of a tide) neither ebbing nor flowing

soon the water will become slack, and the tide will turn

slack tides

the part of a rope or line which is not held taut; the loose or unused part

I picked up the rod and wound in the slack

a spell of inactivity or laziness

he slept deeply, refreshed by a little slack in the daily routine

casual trousers

he put on a grey shirt and loose cotton slacks

loosen (something, especially a rope)

slacking the outhaul allows you to adjust the sail

decrease or reduce in intensity, quantity, or speed

the flow of blood slacked off

the horse slacked his pace

work slowly or lazily

she ticked off her girls if they were slacking

slake (lime)

150 sacks of lime were slacked by the inrushing water

coal dust or small pieces of coal

the fire was stoked with a mixture of slack and cement