Source : Webster's Revised Unabridged Dictionary (1913)

Incredibility \In*cred`i*bil"i*ty\, n. [L. incredibilitas: cf.
   F. incr['e]dibilit['e].]
   1. The quality or state of being incredible; incredibleness.
      --Dryden.

   2. That which is incredible. --Johnson.

Source : WordNet®

incredibility
     n : the quality of being incredible [syn: {incredibleness}]
         [ant: {credibility}]