Source : Webster's Revised Unabridged Dictionary (1913)

Imperfectibility \Im`per*fec`ti*bil"i*ty\, n.
   The state or quality of being imperfectible. [R.]

Source : WordNet®

imperfectibility
     n : the incapability of becoming perfect [syn: {imperfectability}]
         [ant: {perfectibility}]