/ Dictionary / Index A acritarch: Meaning and Definition of Find definitions for: ac•ri•tarch Pronunciation: (ak'ri-tärk"), [key] — n. Paleontol. any of various microfossils, of unknown biological affinities, having a central cavity enclosed by a wall of chiefly organic composition. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. acrimony acritical Related Content Daily Word Quiz: fresco Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language