/ Dictionary / Index A argillite: Meaning and Definition of Find definitions for: ar•gil•lite Pronunciation: (är'ju-līt"), [key] — n. any compact sedimentary rock composed mainly of clay materials; clay stone. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: argillite (Thesaurus) argillaceous arginase Related Content Daily Word Quiz: resilient Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language