The Collaborative International Dictionary of English v.0.48:

Miasma \Mi*as"ma\, n.; pl. Miasmata. [NL., fr. Gr. ?
   defilement, fr. ? to pollute.]
   Infectious particles or germs floating in the air; air made
   noxious by the presence of such particles or germs; noxious
   effluvia; malaria.
   [1913 Webster]

WordNet (r) 3.0 (2006):

miasma
    n 1: an unwholesome atmosphere; "the novel spun a miasma of
         death and decay" [syn: miasma, miasm]
    2: unhealthy vapors rising from the ground or other sources;
       "the miasma of the marshes"; "a miasma of cigar smoke" [syn:
       miasma, miasm]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "miasma":
   BO, afterdamp, bad breath, bad smell, blackdamp, body odor, breath,
   chokedamp, cloud, coal gas, damp, effluvium, exhalation, exhaust,
   exhaust gas, fetid air, fetidity, fetidness, fetor, firedamp,
   flatus, fluid, foul breath, foul odor, frowst, fume, graveolence,
   halitosis, malaria, malodor, mephitis, nidor, noxious stench,
   offensive odor, puff of smoke, reek, reeking, rotten smell, smoke,
   smudge, steam, stench, stench of decay, stink, vapor, volatile,
   water vapor