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Meaning of Dear John

Dear' John'

Pronunciation: [key]
— Informal. Informal.
  1. 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.
  2. any letter terminating a relationship.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.