chicken out

(verb) to be too scared to do something

Example Sentences:

A: Are you going to smoke marijuana, or are you going to chicken out?
B: Leave me alone!

I wanted to go bungee jumping, but I chickened out at the last second, and couldn’t do it.

The group members were upset, because their classmate was always chickening out before giving important presentations.

Media:

Similar idioms:

1. chicken
2. chicken scratch
3. the pot calling the kettle black