back-load
n.— «AHTSVs are offshore supply vessels used in offshore oil exploration and production. They supply materials such as potable water, cement, fuel, food-boxes, equipment and spares to drilling rigs and offshore installations. On their return voyage to the supply base they bring cargo, also termed “back-load” from offshore installations. They are also used to tow drilling rigs from one location to another.» —“Colombo Dockyard set to win order from Shipping Corp” by P. Manoj Livemint May 24, 2007. (source: Double-Tongued Dictionary)