noun
1. : a mold or fungus like a mold with dark mycelium or spores: as
a. : a fungus of the order Mucorales ; especially : the common bread mold ( Rhizopus stolonifer ) — compare mold V
b. : a sooty mold of the families Perisporiaceae and Capnodiaceae
c. : an imperfect fungus of the family Dematiaceae
2. : a diseased and blackened condition produced by a black mold ; especially : a disease of roses that is caused by a fungus ( Chalaropsis thielavioides ) and that causes serious losses in rose grafts especially on Manetti stock by growing over the cut surface of the scion and thus preventing proper union