The Collaborative International Dictionary of English v.0.48:

Bombast \Bom"bast\ (b[o^]m"b[.a]st or b[u^]m"b[.a]st; 277), n.
   [OF. bombace cotton, LL. bombax cotton, bombasium a doublet
   of cotton; hence, padding, wadding, fustian. See
   Bombazine.]
   1. Originally, cotton, or cotton wool. [Obs.]
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            A candle with a wick of bombast.      --Lupton.
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   2. Cotton, or any soft, fibrous material, used as stuffing
      for garments; stuffing; padding. [Obs.]
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            How now, my sweet creature of bombast! --Shak.
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            Doublets, stuffed with four, five, or six pounds of
            bombast at least.                     --Stubbes.
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   3. Fig.: High-sounding words; an inflated style; language
      above the dignity of the occasion; fustian.
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            Yet noisy bombast carefully avoid.    --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Bombast \Bom"bast\, a.
   High-sounding; inflated; big without meaning; magniloquent;
   bombastic.
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         [He] evades them with a bombast circumstance,
         Horribly stuffed with epithets of war.   --Shak.
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         Nor a tall metaphor in bombast way.      --Cowley.
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The Collaborative International Dictionary of English v.0.48:

Bombast \Bom*bast"\ (b[o^]m*b[.a]st" or b[u^]m*b[.a]st"), v. t.
   To swell or fill out; to pad; to inflate. [Obs.]
   [1913 Webster]

         Not bombasted with words vain ticklish ears to feed.
                                                  --Drayton.
   [1913 Webster] Bombastic

WordNet (r) 3.0 (2006):

bombast
    n 1: pompous or pretentious talk or writing [syn: bombast,
         fustian, rant, claptrap, blah]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "bombast":
   absurdity, amphigory, babble, babblement, balderdash,
   bibble-babble, blabber, blather, bluster, boast, boastfulness,
   boasting, bombastry, brag, braggadocio, braggartism, bragging,
   bravado, claptrap, conceit, double-talk, drivel, drool,
   fanfaronade, fiddle-faddle, fiddledeedee, flatulence, flummery,
   folderol, fudge, fustian, gabble, galimatias, gammon, gasconade,
   gasconism, gibber, gibberish, gibble-gabble, gobbledygook,
   grandiloquence, heroics, highfalutin, hocus-pocus, hot air, humbug,
   jabber, jactation, jactitation, jargon, lexiphanicism,
   magniloquence, mumbo jumbo, narrishkeit, niaiserie, nonsense,
   orotundity, pack of nonsense, palaver, prate, prattle, puffery,
   pyrotechnics, rant, rhapsody, rhetoric, rigamarole, rigmarole,
   rodomontade, rubbish, sesquipedality, show, side, skimble-skamble,
   stuff and nonsense, stultiloquence, swagger, trash, trumpery,
   tumidity, turgidity, twaddle, twattle, twiddle-twaddle, vanity,
   vaporing, vaunt, vauntery, vaunting, waffling