pen·i·cil·li·um 
(pĕn′ĭ-sĭlē-əm)
(pĕn′ĭ-sĭlē-əm)n. pl. pen·i·cil·li·ums or pen·i·cil·li·a (-sĭlē-ə)
Any of various characteristically bluish-green fungi of the genus Penicillium that grow as molds on decaying fruits and ripening cheese and are used in the production of antibiotics such as penicillin and in making cheese.
[New Latin Pēnicillium, genus name, from Latin pēnicillus, brush; see PENCIL.]