Necromorphs

Necromorphs are the main enemies of the Dead Space video game franchise and are parasitic alien life-forms that come in a variety of forms ranging from tiny, barely humanoid monstrosities to hulking abominations - they are capable of infecting dead bodies in order to make new Necromorphs and are highly resistant to damage: the best means of defeating most Necromorphs is dismemberment, also in order to prevent new Necromorphs from spawning it is wise for a player to destroy any corpses they come across.

Necromorphs are named after "necro" - which means dead and "morph" - which means form.. making their literal name "dead forms": as their name implies Necromorphs are similiar in many ways to zombies but are not undead - instead they are a unique form of alien life but are just as dangerous to the living due to their desire to spread and their parasitic nature.

According to an in-game description two types of Necromorphs exist, those that exist to infest dead bodies and those that exist to create new corpses - in other words Necromorphs kill other species in order to survive.