noun
: any of several plant diseases in which the top growth undergoes characteristic alteration: as
a. : a disease of citrus that occurs on alkaline soils, that is marked by loss of mature leaves, stiff brushy terminal growth, and abnormal fruits, and that may be related to or a form of stubborn disease
b. : a disease of corn that is prob. due to a virus and that is characterized by the appearance of vegetative shoots often in bunches in place of floral organs
c. : a disease of almonds that is probably caused by a virus and is characterized by growth failure of many flower and leaf buds resulting in a sparse open tree with little fruit