To chicken out is to lose your courage at the last moment and not do it. Chicken out of the jump, nearly chicken out, do not chicken out.
It is informal and mocking, and it always implies the thing was possible. The chicken in it is the old slang for a coward, which English has used for centuries.
1phrasechicken outTo lose your courage at the last moment and not do it.
“He said he would sing and then chicken out at the door.”
chicken out is a phrase.
Practised in Phrasal Verbs