I mean literally. Terrible movies that, due to the time you watched them (mostly childhood or adolescence) you have large swaths of in your memories.
Mine include:
Police Academy 2, especially Mahoney's Jughead/Fudpuckers bit and nearly everything that Bobcat Goldthwait said.
Moving Violations, a little-seen Bill Murray's brother's vehicle
I suppose I'm lucky that somehow I never learned any dialogue from Ice Pirates.
I'll add more later. Speaking of the pharmaceutical industry, why can't they invent something to erase these from my mind.