We don't have synonyms for dump trucks yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are dump truck, dumptruck and dumper trucks.
(n) :
A heavy truck, for carrying loose, bulk cargo (e.g., soil, gravel, grain), having a hinged bed that allows the contents to be unloaded onto the ground via dumping.
(n) :
A heavy truck, for carrying loose, bulk cargo (e.g., soil, gravel, grain), having a hinged bed that allows the contents to be unloaded onto the ground via dumping.