betrayernoun [ C ]
uk/bɪˈtreɪ.ər//bɪˈtreɪ.ɚ/betrayer noun [ C ] (NOT LOYAL)
a person who is not loyal to their country or to another person, often doing something harmful such as giving information to an enemy:
betrayers of the nation's interests
Judas Iscariot is remembered as Christ's betrayer.
betrayer noun [ C ] (REVEALING STH)
something that shows someone's true feelings, thoughts, or character without them intending it:
She hadn't realized her eyes were such betrayers of her internal turmoil.