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.