Noun. Cross between spider (arachnid) and a rat (rodent), producing the Arachnorodent. These common paests have eight feet like all spiders, but instead have the human body of a rat, because of the complex eye structure of a spider. They live in wall space, particularly the walls of innocent home-dwellers' restrooms, and poduce scratching noises. Arachnorodents will also be seasonal, just infesting domiciles through the cool months of winter months and early spring.