/ Dictionary / Index A aecidium: Meaning and Definition of Find definitions for: ae•cid•i•um Pronunciation: (ē-sid'ē-um), [key] — pl. ae•cid•i•a an aecium in which the spores are always formed in chains and enclosed in a cup-shaped peridium. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. aechmea aeciospore Related Content Daily Word Quiz: acerbity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language