The art of removing words from a sentence (or a sentence from a paragraph) to change its context completely. Used commonly in movie posters when a film critic in their review has said something uncomplimentary. Also known as "false attribution" and is related closely to "quotation mining".
A movie or theatre critic may have reviewed the piece saying "The whole thing was a terrific bore, I laughed out loud at the ineptitude of the actors..."
The contextomy on the poster would then read: "Terrific! I laughed out loud!"