The Collaborative International Dictionary of English v.0.48:

Brag \Brag\, v. i. [imp. & p. p. Bragged; p. pr. & vb. n.
   Bragging.] [OE. braggen to resound, blow, boast (cf. F.
   braguer to lead a merry life, flaunt, boast, OF. brague
   merriment), from Icel. braka to creak, brak noise, fr. the
   same root as E. break; properly then, to make a noise, boast.
   ?95.]
   To talk about one's self, or things pertaining to one's self,
   in a manner intended to excite admiration, envy, or wonder;
   to talk boastfully; to boast; -- often followed by of; as, to
   brag of one's exploits, courage, or money, or of the great
   things one intends to do.
   [1913 Webster]

         Conceit, more rich in matter than in words,
         Brags of his substance, not of ornament. --Shak.
   [1913 Webster]

   Syn: To swagger; boast; vapor; bluster; vaunt; flourish; talk
        big.
        [1913 Webster]

WordNet (r) 3.0 (2006):

bragging
    adj 1: exhibiting self-importance; "big talk" [syn: boastful,
           braggart(a), bragging(a), braggy, big,
           cock-a-hoop, crowing, self-aggrandizing, self-
           aggrandising]
    n 1: an instance of boastful talk; "his brag is worse than his
         fight"; "whenever he won we were exposed to his gasconade"
         [syn: brag, bragging, crow, crowing, vaporing,
         line-shooting, gasconade]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "bragging":
   Gascon, bluster, boast, boastful, boastfulness, boasting, bombast,
   brag, braggadocio, braggart, braggartism, bravado, conceit,
   conceited, fanfaron, fanfaronade, fanfaronading, gasconade,
   gasconading, gasconism, heroics, jactation, jactitation,
   rodomontade, self-advertising, self-applauding, self-flattering,
   self-glorious, self-lauding, self-vaunting, side, swagger,
   thrasonic, thrasonical, vain, vainglorious, vanity, vaporing,
   vaunt, vauntery, vaunting