The Collaborative International Dictionary
ureid
Ureide \U"re*ide\, n. (Chem.) Any one of the many complex derivatives of urea; thus, hydantoin, and, in an extended dense, guanidine, caffeine, et., are ureides. [Written also ureid.]
Wiktionary
ureid
n. (context dated organic chemistry English) Any of several classes of (mostly heterocyclic) compounds derived from urea