The Collaborative International Dictionary of English v.0.48:

Talkative \Talk"a*tive\, a.
   Given to much talking.
   [1913 Webster]

   Syn: Garrulous; loquacious. See Garrulous.
        [1913 Webster] -- Talk"a*tive*ly, adv. --
        Talk"a*tive*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

talkativeness
    n 1: the quality of being wordy and talkative [syn: garrulity,
         garrulousness, loquaciousness, loquacity,
         talkativeness]