What is "ambrosia trifida"

Ragweed \Rag"weed`\ (r[a^]g"w[=e]d`), 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, called giant ragweed, is a species of flowering plant in the sunflower family. It is native to North America, where it is widespread in Canada, the United States, and northern Mexico. It is present in Europe and Asia as an introduced species, and it is known as a common weed in many regions. Its common names include great ragweed, Texan great ragweed, giant ragweed, tall ragweed, blood ragweed, perennial ragweed, horseweed, buffaloweed, and kinghead.