A bugbear is a legendary creature roughly analogous with the bogeyman, bogie, bugaboo, hobgoblin and other creatures used to frighten children. Using the term euphemistically in a more modern context, a bugbear is merely an irritant rather than a mythic beast. The Merriam-Webster (http://www.m-w.com/)dictionary defines it as "an imaginary goblin or specter used to excite fear", "an object or source of dread" or "a continuing source of irritation."
In the Dungeons & Dragonsrole-playing game, a bugbear is a humanoid creature similar to the hobgoblin or orc. Bugbears are goblinoid creatures, stronger but less intelligent than hobgoblins.