The Collaborative International Dictionary of English v.0.48:

overblown \o`ver*blown"\, a.
   1. Having been given more publicity than warranted; having
      had ascribed more importance than was justified; as, an
      overblown medical discovery.
      [PJC]

   3. Bombastic, pretentious, or excessive; as, overblown
      rhetoric.
      [PJC]

WordNet (r) 3.0 (2006):

overblown
    adj 1: 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]
    2: past the stage of full bloom; "overblown roses"

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "overblown":
   arty, aureate, big, bloated, bombastic, bursting, choked,
   congested, corpulent, crammed, crowded, declamatory, distended,
   drenched, dropsical, euphuistic, fat, filled to overflowing,
   flatulent, fleshy, flowery, glutted, gorged, grandiloquent, gross,
   heavy, hyperemic, imposing, in spate, jam-packed, jammed,
   magniloquent, obese, oratorical, over the hill, overburdened,
   overcharged, overfed, overflowing, overfraught, overfreighted,
   overfull, overladen, overloaded, overripe, overstocked,
   overstuffed, oversupplied, overweight, overweighted, packed,
   plethoric, portly, ready to burst, running over, satiated,
   saturated, soaked, sonorous, stout, stuffed, stuffed up,
   supercharged, supersaturated, surcharged, surfeited, swollen,
   tumescent, tumid, turgid, windy