Source : WordNet®

piggyback
     adv 1: on a railroad flatcar; "the trailer rode piggyback across
            the country" [syn: {pickaback}, {pig-a-back}]
     2: on the back or shoulder or astraddle on the hip; "she
        carried her child piggyback" [syn: {pickaback}, {pig-a-back}]
     v 1: ride on someone's shoulders or back
     2: haul truck trailers loaded with commodities on railroad cars
     3: haul by railroad car
     4: carry on the back or shoulders; "She piggybacked a sick
        classmate to school"
     5: support on the back and shoulders; "He piggybacked her child
        so she could see the show"