/ Dictionary / Index B boulder clay: Meaning and Definition of Find definitions for: boul'der clay" Pronunciation: [key] — Geol. Geol. a glacial deposit consisting chiefly of unstratified clay with embedded boulders. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Boulder Canyon Boulder Dam Related Content Daily Word Quiz: sinister Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language