calm down in WordNet English dictionary

1. make calm or still
   "quiet the dragons of worry and fear"
   calm  calm down  quiet  tranquilize  tranquillize  tranquillise  quieten  lull  still 
   
2. 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."
   calm  calm down  cool off  chill out  simmer down  settle down  cool it 
   
3. become quiet or less intensive
   "the fighting lulled for a moment"
   lull  calm down 
   

calm down in English Wiktionary