'let up' definitions:

Definition of 'let up'

From: WordNet
verb
Become less in amount or intensity; "The storm abated"; "The rain let up after a few hours" [syn: abate, let up, slack off, slack, die away]
verb
Reduce pressure or intensity; "he eased off the gas pedal and the car slowed down" [syn: ease up, ease off, let up]