1. (n.)pyrethrum any of several chrysanthemums, as Chrysanthemum coccineum, having finely divided leaves and showy red, pink, lilac, or white flowers.
2. pyrethrum the dried flower heads of some of these plants, used as an insecticide and in medicine for certain skin disorders.
Etymology: (1555–65; < L: pellitory)
Definition of 'Pyrethrum'
Princeton's WordNet
1. (noun)pyrethrum made of dried flower heads of pyrethrum plants
2. (noun)pyrethrum, Dalmatian pyrethrum, Dalmatia pyrethrum, Tanacetum cinerariifolium, Chrysanthemum cinerariifolium white-flowered pyrethrum of Balkanarea whose pinnate leaves are white and silky-hairy below; source of an insecticide; sometimes placed in genusChrysanthemum
3. (noun)painted daisy, pyrethrum, Tanacetum coccineum, Chrysanthemum coccineum spring-flowering gardenperennial of Asiaticorigin having finely divided aromatic leaves and white to pink-purple flowers; source of an insecticide; sometimes placed in genusChrysanthemum
4. (noun)Pyrethrum, genus Pyrethrum used in former classifications for plants later placed in genusChrysanthemum and now often included in genusTanacetum
Definitions of Pyrethrum 
