Mawson, C.O.S., ed. (1870–1938). Roget’s International Thesaurus. 1922.

   NOUN:OPACITY; opaqueness &c. adj.; obfuscation, fuliginosity, nubilation.
  film; cloud [See Bubble, Cloud].
   VERB:BE OPAQUE &c. adj.; obstruct the passage of light; obfuscate, offuscate [obs.].
   ADJECTIVE:OPAQUE, impervious to light; adiaphanous; dim [See Dimness]; turbid, thick, muddy, opacous [obs.], obfuscated, fuliginous, cloudy, nubilous, nubilose [obs.], foggy, vaporous, nubiferous.
  SMOKY, fumid [obs.], murky or mirky, smeared, dirty.