WordNet (r) 3.0 (2006):

hot air
    n 1: air that has been heated and tends to rise
    2: loud and confused and empty talk; "mere rhetoric" [syn:
       palaver, hot air, empty words, empty talk,
       rhetoric]

Moby Thesaurus II by Grady Ward, 1.0:

84 Moby Thesaurus words for "hot air":
   babble, babblement, balderdash, baloney, bavardage, bibble-babble,
   big talk, bilge, blab, blabber, blah, blah-blah, blather, blether,
   blethers, bombast, bombastry, bop, bosh, bull, bullshit, bunk,
   bunkum, cackle, caquet, caqueterie, chat, chatter, chitter-chatter,
   clack, clatter, crap, fancy talk, fine talk, fire storm,
   fish story, flapdoodle, fustian, gab, gabble, gas, gibber,
   gibble-gabble, gobbledygook, gossip, guff, gup, highfalutin,
   highfaluting, hogwash, hokum, hooey, idle talk, jabber, malarkey,
   mere talk, moonshine, natter, nonsense talk, palaver, piffle,
   poppycock, prate, prating, prattle, prittle-prattle, rant,
   rodomontade, rot, scat, shit, superheated air, talkee-talkee,
   tall story, tall talk, thermal, tittle-tattle, tommyrot, tripe,
   twaddle, twattle, wind, yak, yakkety-yak