A person who is cowardly or timid; someone who lacks courage (often used disparagingly).
危ないときに逃げるなんて臆病者だと言われた。
He was called a coward for running away when it was dangerous.
臆病者扱いされたのが悔しくて、彼は挑戦を決めた。
Offended at being treated as a coward, he decided to take on the challenge.
子どもに『臆病者』と言うのはやめなさい。
Don't call children 'cowards'.