/ Dictionary / Index C cystidium: Meaning and Definition of Find definitions for: cys•tid•i•um Pronunciation: (si-stid'ē-um), [key] — pl. cys•tid•i•a (in certain basidiomycetous fungi) one of the large, inflated, sterile cells growing between the basidia and usually projecting beyond them. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. cystic mastitis cystine 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