Cool off is a common phrase used to describe the process of becoming less agitated or enraged. It is often used in situations where somebody is getting angry or upset and needs to calm down. There are many synonyms for "cool off" that can be used depending on the context or situation. Some of the most common alternatives include "calm down," "take a breather," "chill out," "mellow out," "relax," "unwind," "de-stress," "let go," "compose oneself," "collect oneself," "soothe," "pacify," and "restrain." Each of these words and phrases carries a slightly different connotation, but they all communicate the same basic idea of needing to reduce stress and tension.