noun
1. : a dark or black velvety coating of mycelium of various fungi growing in insect honeydew on the leaves, fruit, or other exposed parts of plants, when heavy often interfering with the normal metabolism of the plant, and being especially common on plants of the genus Citrus
2. : a fungus (as members of the family Capnodiaceae and Meliolaceae) that causes or develops as a sooty mold on plants