› [U] the fact that something is too loose: There's too much slack in these ropes. The men pulled on the ropes to take up the slack (= to tighten them).
slack noun [U]
› the state of being too loose or not tight enough: There was too much slack in the cable.
› someone who is slack is not working hard enough or spending enough time or care on something: Businesses that shout loudest about delayed payments are often the worst slack payers.be slack with something She's always been a bit slack with her accounts.