/ Dictionary / Index P penicillium: Meaning and Definition of Find definitions for: pen•i•cil•li•um Pronunciation: (pen"u-sil'ē-um), [key] — pl. -cil•li•ums, -cil•li•a any fungus of the genus Penicillium, certain species of which are used in cheesemaking and as the source of penicillin. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: penicillium (Thesaurus) penicillin peninsula Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language