pyrethrum

[pahy-ree-thruh m, -reth-ruh m]
noun
  1. any of several chrysanthemums, as Chrysanthemum coccineum, having finely divided leaves and showy red, pink, lilac, or white flowers, cultivated as an ornamental.
  2. any of several chrysanthemums, as C. cinerariifolium, or C. coccineum, cultivated as a source of insecticides.
  3. Pharmacology. the dried flower heads of these plants, used chiefly as an insecticide and sometimes in medicine for certain skin disorders.

Origin of pyrethrum

1555–65; < Latin: pellitory < Greek pýrethron, akin to pyretós fever; compare pellitory
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for pyrethrum

pyrethrum

noun
  1. any of several cultivated Eurasian chrysanthemums, such as Chrysanthemum coccineum and C. roseum, with white, pink, red, or purple flowers
  2. any insecticide prepared from the dried flowers of any of these plants, esp C. roseum

Word Origin for pyrethrum

C16: via Latin from Greek purethron feverfew, probably from puretos fever; see pyretic
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012