BASE jumping is an extreme sport that is more extreme than most.
While Brits might think a BASE jumper is a new kind of sweater (which it is), that person is a participant in the sport of jumping off tall things: Buildings, Antennae, Structures and Earth (mountain cliffs and suchlike). This is not to be confused with BRAT: Bananas, Rice, Applesauce and Toast, even though either situation can be preceded by a case of diarrhea.
BASE jumping was invented by Wile E. Coyote. An innovative experimenter, he pioneered the use of a leaf, a sheet of paper, a slow-opening parachute and air resistance, which are seldom used today. BASE jumpers today prefer not to be smashed to bits on landing, throwing the sport's inclusion into the "extreme" category into doubt.
All BASE jumpers must have a Go-Pro or other similar camera to record their deeds for posterity and the police. Most BASE jumpers prefer using a specialized parachute while some prefer to assume a passing giant eagle will come to their rescue. A few have wingsuits after being inspired by Rocky and Bullwinkle cartoons. Helmets seem to be optional, since YOU ALL GONNA DIE.