• (n.) A large nocturnal beetle of the genus Lucanus (as L. capreolus, and L. dama), having long, curved upper jaws, resembling a sickle. The grubs are found in the trunks of old trees.
Horn'bug` noun (Zoology) A large nocturnal beetle of the genus Lucanus (as Latin capreolus , and Latin dama ), having long, curved upper jaws, resembling a sickle. The grubs are found in the trunks of old trees. 
Hornbug is American slang for someone obsessed with sex.