C.H.U.D. is an acronym for Cannibalistic Humanoid Underground Dwellers and are homeless people who have been mutated by radioactive waste into flesh-eating maniacs. They live underground and so there are monsters lurking beneath the streets, beings that were once human, since mutated, and preying on those homeless who live beneath the streets...and guess what? Given the recent drop in the underground transient population, the creatures have resorted to coming to the surface (through sewer manholes) in order to feed.......

"Cannibalism" (from Spanish caníbal, in connection with alleged cannibalism among the Caribs), also called anthropophagy (from Greek anthropos "man" and phagein "to consume") is the act or practice of humans consuming other humans. In zoology, the term cannibalism is extended to refer to any species consuming members of its own kind.

The term "humanoid" refers to any being whose body structure resembles that of a human. In this sense, the term indeed describes primates, as well as mythological creatures and artificial organisms, especially in the context of science fiction and fantasy. An android or is a humanoid robot designed to look like a specific gender, although the words are, in principle, synonymous.

"Underground" as an adjective commonly refers to something that is either below the ground (as opposed to groundlevel or aboveground) or outside of public consciousness. Also the only word in the english language that starts with "Und" and ends with "Und" yet in terms of these movies we refer to the sewer systems......

"Dweller" - intr.v. dwelt (dwelt) or dwelled, dwell·ing, dwells