Select the most appropriate meaning of the given idiom.

Chill out

To calm down

The most appropriate meaning of the idiom "chill out" is to calm down. It is a slang expression that means to relax and not be so stressed or angry. It can be used in a variety of contexts, such as when someone is feeling stressed out, angry, or anxious.

The other options are not as appropriate for the meaning of the idiom. "To fight" means to engage in physical conflict, "To be angry" means to feel intense displeasure or hostility, and "To be nervous" means to feel anxious or apprehensive.