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]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "volubility":
   big mouth, candor, communicativeness, conversableness, effusion,
   effusiveness, flow of words, flowing tongue, fluency,
   fluent tongue, flux de bouche, flux de paroles, flux of words,
   frankness, garrulity, garrulousness, gassiness, gift of gab,
   glibness, gregariousness, gush, gushiness, long-windedness,
   loose tongue, loquaciousness, loquacity, openness, prolixity,
   slush, sociability, spate of words, talkativeness, verbosity,
   windiness