Webster's 1913 Dictionary
LET-UP
Let "-*up `, n. Etym: [See Let to forbear. ]
Defn: Abatement; also, cessation; as, it blew a gale for three days without any let-up. [Colloq. ]
Oxford Dictionary
let-up
let-up ▶noun [ in sing. ] informal a pause or reduction in the intensity of something dangerous, difficult, or tiring: there had been no let-up in the eruption.
Oxford Thesaurus
let-up
let-up noun informal there can be no let-up in the war against drugs: abatement, lessening, decrease, diminishing, diminution, subsidence, moderation, decline, relenting, remission, slackening, weakening, relaxation, dying down, easing off, tailing off, tapering off, dropping away /off, ebbing, waning, dwindling; respite, break, interval, hiatus, suspension, cessation, stop, pause, breathing space, lull, interlude, intermission. ANTONYMS continuation, escalation.