If things calm down, or someone or something calms things down, the amount of activity, trouble, or panic is reduced. We will go back to normal when things calm down Neil Howorth, director of the academy, tried to calm things down. = settle down
If you calm down, or if someone calms you down, you become less angry, upset, or excited. Calm down for a minute and listen to me Do not have a drink or take drugs to calm yourself down
become quiet or calm, especially after a state of agitation; "After the fight both men need to cool off "; "It took a while after the baby was born for things to settle down again "