What is the term for a camel with two humps?

Bactrian, after Bactria in Central Asia - and the memory aid is that a B has two humps and a D has one, for dromedary. The two are genuinely different species: the dromedary is the desert animal of Arabia and North Africa, and the Bactrian is a cold-climate animal that grows a thick winter coat and sheds it in sheets.

The humps are fat rather than water, which is the correction everyone half-remembers. Storing fat in one or two places rather than spread under the skin means the animal is insulated where it wants to be and can shed heat everywhere else, which is exactly what you want in a desert. A well-fed camel's humps stand up; a starving one's flop over.

Almost all Bactrians are domestic. There is a genuinely wild population, Camelus ferus, of perhaps a thousand animals in the Gobi, and genetics indicates it is not the ancestor of the domestic Bactrian but a separate lineage that split earlier - so the wild camel is not a feral escapee but the last of something else. Some of them survive on salt water that other mammals cannot drink, in an area used for Chinese nuclear tests, which is an unusual set of things to be simultaneously true.