Something that is piggy-backed (archaically known as pickaback) is something that is riding on the back of something else. To piggy-back (or to go on a piggyback ride) is to ride on someone's back and/or shoulders. A piggyback ride on top of someone's head is called a-teeiss. People may give piggybacks to move people, to provide others with elevation or for entertainment.
One common piggyback involves the carried person sitting on the carrier's shoulders
with each leg positioned on each side of the carrier's neck and dangling downwards. Alternatively the carried person is positioned lower laterally along the carrier's back
, with their legs extending forward to provide balance
and to possibly be supported by the carrier's arms. Another method of support for the latter method is for the carrier to stick his or her hands underneath the carried person's rear end. The latter position requires less physical strength
and is safer for both persons, however by being positioned on one's shoulders the carried person's weight is evenly balanced and thus over time is less exhausting.
This expression is used by analogy in several contexts, such as in ophthalmology
, electrical engineering
, computer engineering
, computer science
, structural geology
and variuos transport systems, e.g. rail transport
, air transport
and intermodal freight transport
. An example in air transport is the Short Mayo Composite
, in which a smaller aircraft, the "Mercury", was carried aloft on the back of the larger "Maia"; this enabled the Mercury to achieve a greater range than would have been possible had it taken off under its own power. In space transportation systems a satellite on the top of a launcher assembly is said to be "piggybacked" on the launcher. In electrical engineering a secondary integrated circuit may be piggy-backed onto a primary one e.g. to replace without soldering. If the second chip is mounted leads up, the primary IC is said to be dead-roached
instead, since it looks like a dead cockroach
with legs up.
The term piggy-back is also used for a product distribution strategy, where two companies that have product lines that complement each other grant access to each other's distribution channel structures so they may both expand their markets (e.g. abroad). This is a variation to the principle of cross selling.
In rail transport, the practice of carrying trailers, semi-trailers or containers in a train atop a flatcar (intermodal freight transport) is referred to as "piggy-backing." (See Autorack).
It is also possible to carry a railway wagon of one gauge on a flat railway wagon of another gauge; indeed, whole trains of one gauge can be carried on a train of flat wagons of another gauge as was done temporarily in Australia during the 1950s.