[syn: miasmal, miasmic, vaporous, vapourous]
The Collaborative International Dictionary of English v.0.48:
Vaporous \Va"por*ous\ (v[=a]"p[~e]r*[u^]s`), a. [L. vaporosus:
   cf. F. vaporeux.]
   [1913 Webster]
   1. Having the form or nature of vapor. --Holland.
      [1913 Webster]
   2. Full of vapors or exhalations. --Shak.
      [1913 Webster]
            The warmer and more vaporous air of the valleys.
                                                  --Derham.
      [1913 Webster]
   3. Producing vapors; hence, windy; flatulent. --Bacon.
      [1913 Webster]
            The food which is most vaporous and perspirable is
            the most easily digested.             --Arbuthnot.
      [1913 Webster]
   4. Unreal; unsubstantial; vain; whimsical.
      [1913 Webster]
            Such vaporous speculations were inevitable.
                                                  --Carlyle.
      [1913 Webster]
WordNet (r) 3.0 (2006):
vaporous
    adj 1: so thin as to transmit light; "a hat with a diaphanous
           veil"; "filmy wings of a moth"; "gauzy clouds of
           dandelion down"; "gossamer cobwebs"; "sheer silk
           stockings"; "transparent chiffon"; "vaporous silks" [syn:
           diaphanous, filmy, gauzy, gauze-like, gossamer,
           see-through, sheer, transparent, vaporous,
           vapourous, cobwebby]
    2: resembling or characteristic of vapor; "vaporous clouds"
       [syn: vaporific, vapourific, vaporish, vapourish,
       vaporous, vapourous]
    3: filled with vapor; "miasmic jungles"; "a vaporous bog" [syn:
       miasmal, miasmic, vaporous, vapourous]
Moby Thesaurus II by Grady Ward, 1.0:
79 Moby Thesaurus words for "vaporous":
   adulterated, aerial, aerodynamic, aerostatic, aery, air-built,
   airy, attenuate, attenuated, chimeric, chimerical, cloud-born,
   cloud-built, cloud-woven, cloudy, cut, dilute, diluted, dreamlike,
   ethereal, fanciful, fatuitous, fatuous, fine, flimsy, foggy,
   fuming, fumy, gaseous, gasified, gasiform, gaslike, gassy,
   gossamery, illusory, imaginary, insubstantial, mephitic, miasmal,
   miasmatic, miasmic, misty, mushy, oxyacetylene, oxygenous, ozonic,
   phantasmal, phantomlike, pneumatic, rare, rarefied, reeking, reeky,
   shadowy, slight, smoking, smoky, spirituous, steaming, steamy,
   subtile, subtle, tenuous, thin, thinned, thinned-out, uncompact,
   uncompressed, unreal, unsubstantial, vague, vaporing, vaporish,
   vaporlike, vapory, watered, watered-down, windy, wispy