The Collaborative International Dictionary of English v.0.48:

Boastful \Boast"ful\, a.
   Given to, or full of, boasting; inclined to boast; vaunting;
   vainglorious; self-praising. -- Boast"ful*ly, adv. --
   Boast"ful*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

boastful
    adj 1: exhibiting self-importance; "big talk" [syn: boastful,
           braggart(a), bragging(a), braggy, big,
           cock-a-hoop, crowing, self-aggrandizing, self-
           aggrandising]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "boastful":
   Gascon, arrogant, boasting, braggart, bragging, cock-a-hoop,
   conceited, egotistical, exultant, fanfaron, fanfaronading,
   gasconading, haughty, ostentatious, pretentious, proud,
   rodomontade, self-advertising, self-aggrandizing, self-applauding,
   self-flattering, self-glorious, self-lauding, self-vaunting,
   show-off, swelled-headed, thrasonic, thrasonical, vain,
   vainglorious, vaporing, vaunting