Source : Webster's Revised Unabridged Dictionary (1913)

Bluebeard \Blue"beard\, n.
   The hero of a medi[ae]val French nursery legend, who, leaving
   home, enjoined his young wife not to open a certain room in
   his castle. She entered it, and found the murdered bodies of
   his former wives. -- Also used adjectively of a subject which
   it is forbidden to investigate.

         The Bluebeard chamber of his mind, into which no eye
         but his own must look.                   --Carlyle.

Source : WordNet®

Bluebeard
     n : (fairytale) a monstrous villain who marries seven women; he
         kills the first six for disobedience