The Collaborative International Dictionary of English v.0.48:

Grandiloquent \Gran*dil"o*quent\, a. [L. grandis grand + logui
   to speak.]
   Speaking in a lofty style; pompous; bombastic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

grandiloquent
    adj 1: lofty in style; "he engages in so much tall talk, one
           never really realizes what he is saying" [syn:
           grandiloquent, magniloquent, tall]
    2: puffed up with vanity; "a grandiloquent and boastful manner";
       "overblown oratory"; "a pompous speech"; "pseudo-scientific
       gobbledygook and pontifical hooey"- Newsweek [syn:
       grandiloquent, overblown, pompous, pontifical,
       portentous]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "grandiloquent":
   Gongoresque, Johnsonian, affected, aggrandized, amplified, aureate,
   ballyhooed, bedizened, big-sounding, bloated, bombastic,
   convoluted, declamatory, disproportionate, elevated, euphuistic,
   exaggerated, excessive, exorbitant, extravagant, extreme,
   flamboyant, flaming, flashy, flatulent, flaunting, flowery, formal,
   fulsome, garish, gassy, gaudy, grandiose, grandisonant,
   high-flowing, high-flown, high-flying, high-sounding, highfalutin,
   hyperbolic, inflated, inkhorn, inordinate, labyrinthine,
   lexiphanic, lofty, lurid, magnified, magniloquent, meretricious,
   orotund, ostentatious, overblown, overdone, overdrawn,
   overelaborate, overemphasized, overemphatic, overestimated,
   overgreat, overinvolved, overlarge, overpraised, oversold,
   overstated, overstressed, overwrought, pedantic, pompous,
   pontifical, pretentious, prodigal, profuse, puffed, rhetorical,
   self-important, sensational, sensationalistic, sententious, showy,
   solemn, sonorous, stilted, stretched, stuffy, superlative, swollen,
   tall, tortuous, touted, tumid, turgid