The Collaborative International Dictionary of English v.0.48:

Volubility \Vol`u*bil"i*ty\, n. [L. volubilitas: cf. F.
   volubilit['e].]
   The quality or state of being voluble (in any of the senses
   of the adjective).
   [1913 Webster]

WordNet (r) 3.0 (2006):

volubility
    n 1: the quality of being facile in speech and writing [syn:
         fluency, volubility, articulateness]