Breadcrumb Home > Dictionary > Index O opacus: Meaning and Definition of Find definitions for: o•pa•cus Pronunciation: (ō-pā'kus), [key] — adj. Meteorol. (of a cloud) dense enough to obscure the sun or moon. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. opacity opah TrendingHere are the facts and trivia that people are buzzing about. Ramadan and Eid al-Fitr 42 Best War Movie Quotes Current Events This Week: March 2023 Recycling Facts William Shakespeare Worst U.S. Forest Fires ✖ Related Content Daily Word Quiz: manoamano Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language