/ Dictionary / Index H halloysite: Meaning and Definition of Find definitions for: hal•loy•site Pronunciation: (hu-loi'sīt, -zīt, ha-), [key] — n. a refractory clay mineral similar in composition to kaolinite. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Hallowmas Hall process Related Content Daily Word Quiz: pundit Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language