A shrub or small tree of the family Mimosaceae (Leguminosae); specifically the cassie or popinac, Acacia farnesiana, native to subtropical and tropical America, and naturalized in Australia and elsewhere in the tropics.
Origin
Mid 19th century.
Definition of mimosa bush in US English:
mimosa bush
noun
A shrub or small tree of the family Mimosaceae (Leguminosae); specifically the cassie or popinac, Acacia farnesiana, native to subtropical and tropical America, and naturalized in Australia and elsewhere in the tropics.