One of the mysteries of the English language finally explained.
Any of a group of insecticidal compounds present in pyrethrum flowers.‘pyrethrins can cause allergic reactions’mass noun ‘it contains natural pyrethrin’
- ‘Citrus-oil products, pyrethrin products, as well as those with pyrethrins and diatomaceous earth, may be effective.’
- ‘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.’
- ‘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.’
1920s: from pyrethrum + -in.
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