Source : Webster's Revised Unabridged Dictionary (1913)

Bugaboo \Bug`a*boo"\, Bugbear \Bug"bear`\, n. [See {Bug}.]
   Something frightful, as a specter; anything imaginary that
   causes needless fright; something used to excite needless
   fear; also, something really dangerous, used to frighten
   children, etc. ``Bugaboos to fright ye.'' --Lloyd.

         But, to the world no bugbear is so great As want of
         figure and a small estate.               --Pope.

         The bugaboo of the liberals is the church pray. --S. B.
                                                  Griffin.

         The great bugaboo of the birds is the owl. --J.
                                                  Burroughs.

   Syn: Hobgoblin; goblin; specter; ogre; scarecrow.

Source : WordNet®

bugaboo
     n 1: an imaginary monster used to frighten children [syn: {bogeyman},
           {bugbear}, {boogeyman}, {booger}]
     2: a source of concern; "the old bugaboo of inflation still
        bothers them"