There are numerous synonyms for the phrase "calm down." These include "relax," "chill out," "take it easy," "keep your cool," "compose yourself," "unwind," "settle down," "collect yourself," "tranquilize," "soothe," "pacify," "placate," "mollify," "assuage," "appease," "quieten," and "restrain oneself." Each of these expressions conveys a different sense of controlling one's emotions and preventing oneself from becoming too upset or agitated. By using a synonym, one can vary their language and express themselves more effectively in different situations or to different people.