an annual plant (Centaurea cyanus) of the composite family, with tiny, raylike, white, pink, or blue flowers forming a round head at the top of the stem
See cornflower in American Heritage Dictionary 4
(kôrnˈflouˌər)
noun
An annual Eurasian plant (Centaurea cyanus) in the composite family, cultivated and also naturalized in North America and having showy heads of blue, purple, pink, or white flowers. Also called bachelor's button.