Wiktionary
wuss out
vb. (context slang English) To fail to do something because of cowardice.
Usage examples of "wuss out".
This loser's been stuck on this same rep for a month and he's about to wuss out again.
Savich was sitting in a chair by the small cubicle door, his legs crossed, his hands folded across his chest, looking at her, daring her to wuss out on him.