Retroactive anger is any anger that results from reviewing something after the fact and not being upset about it in a timely fashion.
If you are going to give feedback to someone, make it timely. Making a vague statement like “I heard about what you said a few weeks ago, we need to talk about that eventually” is the worst way to give someone effective feedback.
Have you been a victim of “retroactive anger”? Tell us your story anonymously at firstname.lastname@example.org