The act of carrying something piggyback.

Ride on someone's shoulders or back.

Haul truck trailers loaded with commodities on railroad cars.

Haul by railroad car.

Support on the back and shoulders.

Bring into alignment with.

On a railroad flatcar:
— The trailer rode piggyback across the country.

synonyms: pickaback, pig-a-back.

On the back or shoulder or astraddle on the hip:
— She carried her child piggyback.

synonyms: pickaback, pig-a-back.