any of a genus (Spiraea) of shrubs of the rose family, with dense clusters of small, pink or white flowers
See spirea in American Heritage Dictionary 4
also spi·rae·a(spī-rēˈə)
noun
Any of various shrubs of the genus Spiraea of the rose family, having clusters of small white or pink flowers and including the bridal wreath, hardhack, and meadowsweet.