BASE jumping is the recreational sport of jumping from fixed objects, using a parachute to descend to the ground. BASE is an acronym that stands for four categories of fixed objects from which one can jump: buildings, antennas, spans (bridges) and earth (cliffs). Participants jump from a fixed object such as a cliff and after an optional freefall delay deploy a parachute to slow their descent and land. A popular form of BASE jumping is wingsuit BASE jumping.