From Longman Business Dictionary
piggybackpig·gy·back /ˈpɪgibæk/ verb1[intransitiveI, transitiveT] to use a situation that already exists in order to do or get what you wantpiggyback on/ontoSome pharmaceutical companies piggyback on existing brands by borrowing parts of their names.
It wants to piggyback its order onto another city’s contract to keep costs down.
2[transitiveT]TRANSPORT to move goods from one place to another, using containers that can be carried both by train and by road