hawk-weed: A genus of the polygamia superflua order, belonging to the syngenesia class of plants; and in the natural method ranking under the 49th order, Compositae. The receptacle is naked; the calyx calyculated with deciduous scales; the pappus feathery and stalked. There are 14 species, most of them herbaceous annuals, rising to the height of a foot or a foot and an half; and having their branches terminated by ligulated compound red and yellow flowers. These are very large, and consist of many flat florets spread over one another imbrication, and when fully blown appear as if radiated. They are very conspicuous and beautiful: and appear in June, July, and August. They are succeeded by plenty of seed, which, if permitted to scatter on the ground, will produce a number of young plants without further trouble.