pyrethrin

noun

py·​re·​thrin pī-ˈrē-thrən How to pronounce pyrethrin (audio) -ˈre- How to pronounce pyrethrin (audio)
: either of two oily liquid esters C21H28O3 and C22H28O5 having insecticidal properties and occurring especially in the flowers of pyrethrum

Examples of pyrethrin in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The residual sprays can protect your house for up to 45 days, while the pyrethrins, which are short-contact sprays, will irritate the bugs and send them into the residual spray. — Nafeesah Allen, Better Homes & Gardens, 4 Jan. 2025 Complicating matters further is the fact that lice appear to have evolved some resistance to pyrethrin and permethrin, the active ingredients in many over-the-counter lice shampoos. — Anna North, Vox, 7 Dec. 2018

Word History

Etymology

International Scientific Vocabulary, from Latin pyrethrum

First Known Use

1882, in the meaning defined above

Time Traveler
The first known use of pyrethrin was in 1882

Browse Nearby Words

pyret-
pyrethrin
pyrethroid
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Cite this Entry

“Pyrethrin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/pyrethrin. Accessed 20 Apr. 2025.

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Medical Definition

pyrethrin

noun
py·​re·​thrin pī-ˈrē-thrən How to pronounce pyrethrin (audio) -ˈreth-rən How to pronounce pyrethrin (audio)
: either of two oily liquid esters C21H28O3 and C22H28O5 that have insecticidal properties and are the active components of pyrethrum

More from Merriam-Webster on pyrethrin

Britannica.com: Encyclopedia article about pyrethrin

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