/ Dictionary / Index A acanthodian: Meaning and Definition of Find definitions for: ac•an•tho•di•an Pronunciation: (ak"un-thō'dē-un), [key] — n. any small, spiny-finned, sharklike fish of the extinct order Acanthodii, from the Paleozoic Era. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. acanthocytosis acanthoid Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language