/pen'euh sil"ee euhm/ , n. , pl. penicilliums, penicillia /-sil"ee euh/ .
any fungus of the genus Penicillium, certain species of which are used in cheesemaking and as the source of penicillin.
[ 1925-30; penicill ( us ) brush (see PENCIL) + -ium -IUM ]