[pig.gy.back] adv [alter. of earlier a pick pack, of unknown origin] (1565) 1: up on the back and shoulders
2: on or as if on the back of another; esp: on a railroad flatcar
[2]piggyback n (ca. 1590) 1: the act of carrying piggyback
2: the movement of loaded truck trailers on railroad flatcars [3]piggyback adj (1823) 1: marked by being up on the shoulders and back "a child needs hugging, tussling, and ~ rides --Benjamin Spock"
2: carried or transported piggyback: as a: of or relating to the hauling of truck trailers on railroad flatcars b: of, relating to, or being a radio or television commercial that is presented in addition to other commercials during one commercial break c: being or relating to something carried into space as an extra load by a vehicle (as a spacecraft) [4]piggyback vt (1952) 1: to carry up on the shoulders and back
2: to haul (as a truck trailer) by railroad car
3: to set up or cause to function in conjunction with something larger or more important ~ vi 1: to haul truck trailers on railroad cars
2: to function or be carried on or as if on the back of another