noun
1. : any of certain diseases of plants characterized by browning and decay of tissues: as
a. : a disease of stone and pome fruits caused by fungi of the genus Sclerotinia and marked by blighting of twigs, blossoms, and leaves and canker of the stems as well as browning
b. or brown rot gummosis : a destructive disease of citrus fruits caused by a fungus ( Phytophthora citrophthora ) and marked by gummosis of the trunk as well as browning and decay — called also foot rot
c. : a destructive disease of potatoes, tomatoes, tobacco, and related plants caused by a bacterium ( Pseudomonas solanacearum ) and marked by browning of the vascular bundles and wilting — called also ring disease, ring rot, tobacco wilt
d. : a decay of timber caused by a fungus ( Polyporus sulphureus )
2. : any organism causing brown rot