A bungee cord also known as a shock cord, is an elastic

Elastomer

An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred...

 cord composed of one or more elastic strands forming a core, usually covered in a woven cotton or polypropylene

Polypropylene

Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...

 sheath. The sheath does not materially extend elastically, but it is braided with its strands spiraling around the core so that a longitudinal pull causes it to squeeze the core, transmitting the core's elastic compression to the longitudinal extension of the sheath and cord. Specialized bungees, such as some used in bungee jumping

Bungee jumping

Bungee 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...

, may be made entirely of elastic strands.

Bungee cords have been used to provide a lightweight suspension for aircraft undercarriages from before World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, and are still used on many small homebuilt aircraft where weight remains critical. Bungee cords were also used in parachuting

Parachuting

Parachuting, also known as skydiving, is the action of exiting an aircraft and returning to earth with the aid of a parachute. It may or may not involve a certain amount of free-fall, a time during which the parachute has not been deployed and the body gradually accelerates to terminal...

 to assist in opening the old-style parachute container after the ripcord

Ripcord (skydiving)

A ripcord is a part of a skydiving harness-container system; a handle attached to a steel cable ending in a closing pin. The pin keeps the container closed and keeps the spring-loaded pilot chute inside. When the ripcord is pulled, the container is opened and the pilot chute is released, opening...

 was pulled.

Today, bungee cords are most often used to secure objects without tying knot

Knot

A knot is a method of fastening or securing linear material such as rope by tying or interweaving. It may consist of a length of one or several segments of rope, string, webbing, twine, strap, or even chain interwoven such that the line can bind to itself or to some other object—the "load"...

s and to absorb shock

Shock absorber

A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy. It is a type of dashpot.-Nomenclature:...

. Inexpensive bungee cords, with metal or plastic hooks on each end, are marketed as a general utility item. This form is also known as octopus, or "occy", straps in Australia, these can be an individually, or a set of four hooked straps held together by a metal ring allowing the occy strap to secure items around various tie points, for example a suitcase to a car roof rack. Extensions of the concept are available as a coarse net of bungee cords with metal or plastic hooks around the periphery, for securing irregularly shaped loads of luggage and cargo on the backs of pickup truck

Pickup truck

A pickup truck is a light motor vehicle with an open-top rear cargo area .-Definition:...

s, roofs of cars, and so on.

The origin of the name "bungee", "bu" is uncertain. The Oxford English Dictionary

Oxford English Dictionary

The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

 records the use in 1938 of the phrase bungee-launching of gliders

Glider (sailplane)

A glider or sailplane is a type of glider aircraft used in the sport of gliding. Some gliders, known as motor gliders are used for gliding and soaring as well, but have engines which can, in some cases, be used for take-off or for extending a flight...

using an elasticized cord.