Source : Webster's Revised Unabridged Dictionary (1913)

Shameless \Shame"less\, a. [AS. scamle['a]s.]
   1. Destitute of shame; wanting modesty; brazen-faced;
      insensible to disgrace. ``Such shameless bards we have.''
      --Pope.

            Shame enough to shame thee, wert thou not shameless.
                                                  --Shak.

   2. Indicating want of modesty, or sensibility to disgrace;
      indecent; as, a shameless picture or poem.

   Syn: Impudent; unblushing; audacious; immodest; indecent;
        indelicate. -- {Shame"less*ly}, adv. --
        {Shame"less*ness}, n.

Source : WordNet®

shamelessness
     n : behavior marked by a bold defiance of the proprieties and
         lack of shame [syn: {brazenness}]