Source : Webster's Revised Unabridged Dictionary (1913)

Insipidity \In`si*pid"i*ty\, Insipidness \In*sip"id*ness\, n.
   [Cf. F. insipidit['e].]
   The quality or state of being insipid; vapidity. ``Dryden's
   lines shine strongly through the insipidity of Tate's.''
   --Pope.

Source : WordNet®

insipidness
     n : lacking any distinctive or interesting taste property [syn:
         {blandness}, {insipidity}]