The Collaborative International Dictionary of English v.0.48:

Nauseous \Nau"seous\ (?; 277), a. [L. nauseosus.]
   1. Causing, or fitted to cause, nausea; sickening; loathsome;
      disgusting; exciting abhorrence; as, a nauseous drug or
      medicine.
      [1913 Webster]

   2. Feeling nausea; as, nauseous from the effects of
      chemotherapy.
      [PJC] -- Nau"seous*ly, adv. -- Nau"seous*ness, n.
      [1913 Webster]

            The nauseousness of such company disgusts a
            reasonable man.                       --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nauseous
    adj 1: causing or able to cause nausea; "a nauseating smell";
           "nauseous offal"; "a sickening stench" [syn:
           nauseating, nauseous, noisome, queasy,
           loathsome, offensive, sickening, vile]
    2: feeling nausea; feeling about to vomit [syn: nauseated,
       nauseous, queasy, sick, sickish]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "nauseous":
   abhorrent, airsick, anguished, anxious, bad, barfy, bored,
   brackish, carsick, cheerless, cloying, depressed, disgusted,
   disgusting, emetic, fetid, foul, fulsome, grim, high, icky,
   joyless, loathsome, maggoty, mawkish, nasty, nauseant, nauseated,
   nauseating, noisome, noxious, offensive, overripe, pleasureless,
   poisonous, prey to malaise, pukish, puky, qualmish, qualmy, queasy,
   rancid, rank, rebarbative, repelled, repellent, repugnant,
   repulsive, revolted, revolting, rotten, sad, seasick, sickened,
   sickening, spoiled, squeamish, stinking, suffering angst, uneasy,
   unfulfilled, ungratified, unhappy, unpleasant, unquiet,
   unsatisfied, vile, vomity, weevily, yucky