Roget's Thesaurus of English Words and Phrases by Peter Mark Roget

426. Opacity — N. opacity; opaqueness &c adj.. film; cloud &c 353.

V. be opaque &c adj.; obstruct the passage of light; obfuscate, offuscate†. Adj. opaque, impervious to light; adiaphanous†; dim &c 422; turbid, thick, muddy, opacous†, obfuscated, fuliginous†, cloud, hazy, misty, foggy, vaporous, nubiferous†, muggy† &c (turbidity) 426.1. smoky, fumid†, murky, dirty. 426a. Turbidity — N. turbidity, cloudiness, fog, haze, muddiness, haziness, obscurity. nephelometer [instrument to measure turbidity]. Adj. turbid, thick, muddy, obfuscated, fuliginous†, hazy, misty, foggy, vaporous, nubiferous†; cloudy (cloud) 353. smoky, fumid†, murky, dirty.