The Collaborative International Dictionary of English v.0.48:
Let-up \Let"-up`\ (l[e^]t"[u^]p`), n. [See Let to forbear.] Abatement; also, cessation; as, it blew a gale for three days without any let-up. [Colloq.] [1913 Webster]WordNet (r) 3.0 (2006):
letup n 1: a pause during which things are calm or activities are diminished; "there was never a letup in the noise" [syn: letup, lull]