Dear John

noun Informal.

a letter from a woman informing her boyfriend or fiancé that she is ending their relationship or informing her husband that she wants a divorce: Nothing is worse for a soldier's morale than getting a Dear John.
any letter terminating a relationship.

Origin of Dear John

First recorded in 1940–45

Also called Dear John letter. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019