unfriend
1 antonym for unfriend — opposites grouped by meaning.
Noun — One who is not a friend; an enemy.
Antonyms
Etymology
Unfriend comes from Middle English unfreend, onfrend, made up of un- (a noun/adjective prefix) and friend. It is cognate with Scots unfrend (“unfriend”), and compares with Old English unfriþmann and unwine.
Full origin of unfriend →