To ride on someone's back, or to use another person's progress or idea to advance your own.
The origin is debated, but it may come from 'pick-a-back,' describing the way a child picks a ride on someone's back. It entered common English usage in the 1500s.
In biology, 'piggybacking' is how many organisms survive—remora fish literally attach to sharks for transportation, and parasitic wasps lay eggs on other insects that unknowingly carry their babies to new food sources.
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