from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any of various weeds of the genus Ambrosia having small, greenish, unisexual flower heads and producing abundant pollen that is one of the chief causes of hay fever.
- n. Chiefly British Ragwort.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A plant of the genus Ambrosia. These weeds are particularly noted for producing pollen which people with hay fever are allergic to.
from the GNU version of the Collaborative International Dictionary of English
- n. A common American composite weed (Ambrosia artemisiæfolia) with finely divided leaves; hogweed.
from The Century Dictionary and Cyclopedia
- n. Any plant of the composite genus Ambrosia; especially, the common North American species A. trifida, the great ragweed or horse-cane, and A. artemisiæfolia, the Roman wormwood or hogweed.
- n. The ragwort or St.-James-wort, Senecio Jacobæa.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- 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
- n. widespread European weed having yellow daisylike flowers; sometimes an obnoxious weed and toxic to cattle if consumed in quantity
From the ragged shape of its leaves.(American Heritage® Dictionary of the English Language, Fourth Edition)
rag + weed (Wiktionary)