a load transported on the return journey of a delivery truck.
verb
1 [no object] transport a load on a return journey:I get paid for the round trip, even if I don’t backload
2 [with object] place more charges at the later stages of (a financial agreement) than at the earlier stages:the agreement was backloaded (as adjective backloaded)backloaded rentals
backload in other Oxford dictionaries
Definition of backload in the US English dictionary