/ Dictionary / Index M mudstone: Meaning and Definition of Find definitions for: mud•stone Pronunciation: (mud'stōn"), [key] — n. Geol. a clayey rock with the texture and composition of shale but little or no lamination. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mudspringer mud stream Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language