/ Dictionary / Index O oil shale: Meaning and Definition of Find definitions for: oil' shale" Pronunciation: [key] — Geol. Geol. a black or dark-brown shale or siltstone rich in bitumens, from which shale oil is obtained by destructive distillation. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. oilseed oilskin Related Content Daily Word Quiz: jovial Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language