Source : Webster's Revised Unabridged Dictionary (1913)

Demimonde \Dem`i*monde"\, n. [F.; demi + monde world, L.
   mundus.]
   Persons of doubtful reputation; esp., women who are kept as
   mistresses, though not public prostitutes; demireps.

   {Literary demimonde}, writers of the lowest kind.

Source : WordNet®

demimonde
     n : a class of woman not considered respectable because of
         indiscreet or promiscuous behavior