(n) any of numerous chiefly North American weedy plants constituting the genus Ambrosia that produce highly allergenic pollen responsible for much hay fever and asthma, Syn. bitterweed, ambrosia
n. (Bot.) (a) A composite plant (Anthemis Cotula), having a strong odor; dog's fennel. It is a native of Europe, now common by the roadsides in the United States. (b) The feverfew. [ 1913 Webster ]