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Word of the Day
Thursday, August 18, 2016

Definitions for opacus

  1. Meteorology. (of a cloud) dense enough to obscure the sun or moon.

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Citations for opacus
What is the cloudspotter to do when the cloud layer has grown thick enough to be of the opacus, rather than the translucidus, variety, so that it doesn't show the position of the sun or moon? Gavin Pretor-Pinney, The Cloudspotter's Guide: The Science, History, and Culture of Clouds, 2006
The nine cloud varieties are intortus, vertebratus, undulatus, radiatus, lacunosis, duplicatus, translucidus, perlucidus, and opacus. Edited by Douglas M. Considine, Van Nostrand's Scientific Encyclopedia, Eighth Edition, 1994
Origin of opacus
Opacus is a New Latin construction that stems from the Latin opācus meaning "shaded."