n.
Any of about 50 species of strong-smelling, poisonous herbs, especially common tansy ( Tanacetum vulgare , or Chrysanthemum vulgare ), of the composite family , native to the northern temperate zone.
T. vulgare has button-shaped yellow flower heads of disk flowers (no ray flowers) that are arranged in a flat-topped cluster, deeply cut leaves, and many stems. It is sometimes cultivated in herb gardens and was formerly used in medicines and insecticides. See also chrysanthemum .