Pyrethrum (Noun) — Used in former classifications for plants later placed in genus Chrysanthemum and now often included in genus Tanacetum.
Pyrethrum (Noun) — Made of dried flower heads of pyrethrum plants.
Pyrethrum (Noun) — White-flowered pyrethrum of Balkan area whose pinnate leaves are white and silky-hairy below; source of an insecticide; sometimes placed in genus Chrysanthemum.
Pyrethrum (Noun) — Spring-flowering garden perennial of Asiatic origin having finely divided aromatic leaves and white to pink-purple flowers; source of an insecticide; sometimes placed in genus Chrysanthemum.