A plant of the genus Ambrosia. These weeds are particularly noted for producing pollen which people with hay fever are allergic to.
User Defined Definitions
"widespread European weed having yellow daisylike flowers; sometimes an obnoxious weed and toxic to cattle if consumed in quantity"
"any of numerous chiefly North American weedy plants constituting the genus Ambrosia that produce highly allergenic pollen responsible for much hay fever and asthma"