Pyrethrum definition

pī-rēthrəm, -rĕthrəm
An insecticide made from the dried flower heads of any of these plants.
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A Eurasian perennial plant (Tanacetum coccineum) in the composite family, cultivated for its colorful flower heads and formerly used as a source of an insecticide.
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A closely related perennial plant (Tanacetum cinerariifolium), commercially cultivated as the source of an insecticide.
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A perennial plant (Chrysanthemum coccineum) of the composite family, widely grown for the white, pink, red, or purple flower heads.
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An insecticide made from the dried flower heads of several Old World chrysanthemums, esp. a species (Chrysanthemum cinerariaefolium) now grown extensively in the U.S.
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Any of several perennial African plants of the genus Tanacetum, especially Tanecetum cinerariifolium.
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(organic chemistry) Any of several insecticides obtained from these plants; pyrethrin.
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Other Word Forms

Noun

Singular:
pyrethrum
Plural:
pyrethrums

Origin of pyrethrum

  • Latin pellitory (Anacyclus pyrethrum) from Greek purethron from pūr fire (from its warming effect) pyretic

    From American Heritage Dictionary of the English Language, 5th Edition