Definition of pyrethrin in English:

pyrethrin

noun

Chemistry
  • Any of a group of insecticidal compounds present in pyrethrum flowers.

    ‘pyrethrins can cause allergic reactions’
    [mass noun] ‘it contains natural pyrethrin’
    • ‘If the infestation is severe, topically administered permethrin, pyrethrin, or malathion also may help.’
    • ‘If you absolutely have to, you can spray with an insecticidal soap or insecticide that contains pyrethrins.’
    • ‘Citrus-oil products, pyrethrin products, as well as those with pyrethrins and diatomaceous earth, may be effective.’
    • ‘Many of these sprays contain one or more of a group of insecticidal compounds known as pyrethrins.’
    • ‘These synthetic chemicals mimic the action of natural pyrethrins derived from chrysanthemum flowers.’

Origin

1920s: from pyrethrum + -in.

Pronunciation:

pyrethrin

/pʌɪˈriːθrɪn/