Definitions for ragweedˈrægˌwid
Random House Webster's College Dictionary
any of the composite plants of the genus Ambrosia, the airborne pollen of which is the most prevalent cause of autumnal hay fever.
Origin of ragweed:
1650–60; so called from its ragged appearance
ragwort, tansy ragwort, ragweed, benweed, Senecio jacobaea(noun)
widespread European weed having yellow daisylike flowers; sometimes an obnoxious weed and toxic to cattle if consumed in quantity
ragweed, ambrosia, bitterweed(noun)
any of numerous chiefly North American weedy plants constituting the genus Ambrosia that produce highly allergenic pollen responsible for much hay fever and asthma
A plant of the genus Ambrosia. These weeds are particularly noted for producing pollen which people with hay fever are allergic to.
a common American composite weed (Ambrosia artemisiaefolia) with finely divided leaves; hogweed