Bungee jumping also spelled "Bungy" jumping is an activity
that involves jumping from a tall structure while connected to a large elastic
cord. The tall structure is usually a fixed object, such as a building, bridge
or crane; but it is also possible to jump from a movable object, such as
a hot-air-balloon or helicopter, that has the ability to hover above the
ground. The thrill comes as much from the free-falling as from the rebounds.
When the person jumps, the cord stretches and the jumper flies upwards again
as the cord snaps back (not actually snapping though), and continues to oscillate
up and down until all the energy is dissipated.
Source: Wikipedia