Base jumping
The phrase base jumping (the extreme sport of parachuting from the tops of very tall objects, like skyscrapers) doesn’t actually refer to bouncing at the base of a land mass, or pogo sticking around an army base. When followed by the word jumping, base—or, in its capitalized acronym form BASE—stands for “Building, Antenna, Span, and Earth.” These words are the four categories of places true base jumpers will jump from.