a large desert animal with a long neck and either one or two humps(=large raised parts) on its back.——朗文当代大辞典

A large hornless ruminant quadruped, distinguished by its humped back, long neck, and cushioned feet; it is nowhere found wild, but is domesticated in Western Asia and Northern Africa, in the arid regions of which it is the chief beast of burden.——牛津当代大辞典  @en