The Collaborative International Dictionary of English v.0.48:

Bogeyman \Bo"gey*man\, n.; pl. Bogeymen.
   A goblin; a bugbear; a bogey[1]. This is the form used by
   parents to frighten children; as, if you don't eat your
   vegetables, the bogeyman will get you.

   Syn: bogey.
        [Webster 1913 Suppl.]