Regurgitators earn their name because of the odd tactics they use in battle. They will fight melee style, and quite effectively, but their first priority is to waddle around the battlefield, consuming whole the corpses of dead monsters. These they chew up for a moment, before spitting the partially-digested remains at the nearest character or minion. This ability (named Corpse Cannon) deals fairly major physical damage, but can be blocked like any other projectile. Corpses eaten in this way are destroyed, and can not be used by any corpse skills, or resurrected by monster shaman.
One of the most annoying bugs in the history of Diablo II was in the first version after release; at that time Regurgitators could eat the corpses of dead mercenaries, and spit them just like any monster corpse. This was a problem since mercs that were eaten were bugged, and could not be resurrected in any way, permanently losing all equipment on the mercenaries.
Wretched in appearance and manner, these grotesque abominations are created from the bile and flesh of the tortured damned. While their hulking forms can deliver a surprisingly sound blow, it is their ability to devour, rapidly digest and then vomit forth the corpse as a poisonous gobbet that gives them their name.