To piggyback is to have Alpha
seated on Beta
, with Alpha's thighs straddling
. Normally, Alpha will hold Beta around the chest
(or less desirably, the neck
), and Beta will further support Alpha's weight by holding the thighs or knees
. If the pair
, or dance
about, this would be referred to as a piggyback ride
Although both persons can be said to "piggyback", it can be clarified who serves which role in the physical relationship by having Alpha "be given a piggyback by" Beta, and conversely by having Beta "give a piggyback to" Alpha. (Interestingly enough, the role of Alpha is both dominant and submissive.)
Contrast with shoulder ride.
Piggybacking is also used to describe means of transportation which involve a carried mass atop a locomotive mass, as in trains, trucks, and rocket ships.
On a more abstract level, piggybacking is used to descibe an effect which is realised because of another effect, as in chemical processes, governmental legislations, medical trauma, or computer data transfer.