any of a genus (Hydrangea) of shrubs or vines of the saxifrage family, with opposite leaves and large, showy clusters of white, blue, or pink flowers, often sterile
See hydrangea in American Heritage Dictionary 4
(hī-drānˈjə, -drănˈ-)
noun
Any of various shrubs of the genus Hydrangea, having opposite leaves and large, flat-topped or rounded clusters of white, pink, or blue flowers.