Pertaining to transportation of goods where one transportation unit is carried on the back of something else. For example, a truck on a train.
1959 November, J. N. Westwood, “The Railways of Canada”, in Trains Illustrated, page 554, photo caption:
A Montreal-Toronto "Piggyback" freight of the Canadian Pacific.
1960 November, David Morgan, “"Piggyback"—U.S. success story”, in Trains Illustrated, pages 681–682:
What might be termed the psychological break-through for U.S. piggyback came in 1953-54. A prototype 75-foot piggyback flatcar was built, establishing the precedent for today's standard car with a capacity for two road trailers.
1985, John H. Mahoney, Intermodal Freight Transportation:
Until this time the railroads had favored piggyback services […]
Attached or appended to something larger or more important.
They tried to piggyback that proposal on the rivers and harbors bill.
The popular host can’t claim credit for the trade, though. The idea wasn’t his. He piggybacked off another successful investor who had a history of picking winners.
2011Allen Gregory, "1 Night in Gottlieb" (season 1, episode 2):
Allen Gregory DeLongpre: Pat, I gotta tell you, you did a lot of things right with this lunch―kudos. You got back quickly, you showed initiative, and, best of all, you left plenty of room for improvement. Piggybacking on that last part, the ugly business of the critique.
2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, →ISBN, page 81:
[...] having crossed the river, the District again became entwined with the London & South Western Railway. In fact, the District would go from East Putney to Wimbledon by piggybacking on to a branch line of that railway, and sometimes overground trains still use the branch as a relief route between Wimbledon and Clapham Common.
2023 March 22, Nick Brodrick, “Back to the future on the East Lancs?”, in RAIL, number 979, page 44:
But while carrying passengers for recreation is one thing, ferrying bona fide commuters in and out of the UK's third largest city is quite another. Yet that is exactly what Rossendale Borough Council (RBC) wants to do, by piggybacking onto the preserved railway's operations.
(transitive,Internet) To obtain a wirelessinternet connection by bringing one's own computer within the range of another's wireless connection without that subscriber's permission or knowledge.
1960 November, David Morgan, “"Piggyback"—U.S. success story”, in Trains Illustrated, page 683:
American railroads are not permitted to operate long-haul road routes, but the I.C.C. decision of 1954 did permit them to solicit trailer business in, say, New York for Chicago provided the trailer was piggybacked in between.
(transitive) To enter a secured area at the same time along with (someone having authorized access); to tailgate. (Can we add an example for this sense?)
1989, Alice J. Smith, Dosage and Solutions Calculations: The Dimensional Analysis Way, page 258:
Piggyback medications are given through a port of an existing intravenous site. […] Calculation of the drip rate for piggybacks is the same as any other drip rate.
2009, Diane S. Aschenbrenner, Samantha J. Venable, Drug Therapy in Nursing, page 34:
Certain IV drugs, whether given by piggyback or through a metered-dose infusion set, may be incompatible with an existing continuous IV infusion.