» for the capping process in biology see 5' cap. Capping is best to describe the Internet activity of looking at a screen capture (or "screengrab") and typing a caption to coincide with the picture. Usually the caption can be of any use, like observation, but generally it's used to make a humorous quip about the screengrab. History The beginnings It began with the popular cult TV show Mystery Science Theater 3000, whose characters make jokes while watching bad movies. It was a phenomenon of min… (More on Capping)