Various spellings including bungee, bunji, bunjee and bunjy.
Bungy jumping consists of falling from a large height, to which one has been affixed with chords of elastic material. Assuming the jump has been set up correctly, the jumper will have experienced several seconds of free fall, slowed down to rest without hitting the ground, and subsequently bounced back up and down a couple of times dangling from the chords, before being lowered to safety. This is often considered an exhilirating experience for the participant. The jumper is normal assisted by a combined counsellor/saftey supervisor for the jump site called the "Jump Master".
Typical structures include bridges and cranes; more outre jumps may take place from hot air balloons or helicopters.
The original source of this activity is the populace of the island of Vanuatu in the Pacific, members of which have been throwing themselves from huge wooden towers for centuries with a bundle of vines tied to their feet.
Tied in with mythology, the ritual appears to have been used as a death/rebirth rite as well as a general sacramental rite.
A group of writers from National Geographic magazine landed on the island of Penetecost in 1954 and reported on the 'South Seas Incredible Land Divers' who would throw themselves off a high tower made of logs and branches.
The form of Bungy most often practiced today as a "sport" was first attempted by the Oxford University Dangerous Sports Club who made an experimental jump from a 245-high bridge in Bristol, England around 1970.
Despite the inherent danger of jumping from a great height, several million jumps have taken place since 1980 successfully attributable to bungy operators rigorously conforming to standards and guidelines governing jumps, such as double checking calculations and fittings for every jump.
Unfortunately accidents in this sport tend to be of the spectacular, bizzarre and terminal variety, and are often caused by negligence, i.e. a stoned jump-master forgetting to attach the bungy chord to the platform.
There are various more exotic (and usually more dangerous) forms of bungy, such as "catapulting" upwards rather than falling, tandem jumps and "sandbagging", in which the jumper holds a heavy weight which is released at the lowest point of the jump, allowing him/her to bounce back above the jheight of the jump platform.