The Collaborative International Dictionary of English v.0.48:

Hobgoblin \Hob"gob`lin\, n. [See 2d Hob, and Goblin.]
   A frightful goblin; an imp; a bugaboo; also, a name formerly
   given to the household spirit, Robin Goodfellow. --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hobgoblin
    n 1: (folklore) a small grotesque supernatural creature that
         makes trouble for human beings [syn: goblin, hob,
         hobgoblin]
    2: an object of dread or apprehension; "Germany was always a
       bugbear for France"; "A foolish consistency is the hobgoblin
       of little minds"--Ralph Waldo Emerson [syn: bugbear,
       hobgoblin]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "hobgoblin":
   Dracula, Frankenstein, Wolf-man, bogey, bogeyman, bugaboo, bugbear,
   fee-faw-fum, frightener, ghost, ghoul, goblin, hob, holy terror,
   horror, incubus, monster, nightmare, ogre, ogress, ouphe, phantom,
   revenant, scarebabe, scarecrow, scarer, specter, succubus, terror,
   vampire, werewolf