Ragweed \Rag"weed\, n. (Bot.) A common American composite weed ({Ambrosia artemisi[ae]folia}) with finely divided leaves; hogweed. {Great ragweed}, a coarse American herb ({Ambrosia trifida}), with rough three-lobed opposite leaves.
Ambrosia trifida n : a coarse annual with some leaves deeply and palmately 3-cleft or 5-cleft [syn: {great ragweed}]