coward       
noun [ C ]  disapproving uk/ˈkaʊ.əd/ us/ˈkaʊ.ɚd/
B2 胆小鬼,懦夫
a person who is not brave and is too eager to avoid danger, difficulty, or pain
  They branded her a coward for informing on her colleagues during the interrogation. 她在审讯中告发了同事,因此被视为懦夫。 
 - More examples
 - He despised himself for being such a coward.
 - He is a coward and a bully.
 - She considered him a coward for failing to join up in the war.