[ pahy-ree-thrin, -reth-rin ]

  1. Also called pyrethrin I. a viscous, water-insoluble liquid, C21H28O3, extracted from pyrethrum flowers, used as an insecticide.

  2. Also called pyrethrin II. a like compound, C22H28O5, obtained and used similarly.

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Origin of pyrethrin

First recorded in 1830–40; pyrethr(um) + -in2

Words Nearby pyrethrin Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use pyrethrin in a sentence

British Dictionary definitions for pyrethrin


/ (paɪˈriːθrɪn) /

  1. Also called: pyrethrin I an oily water-insoluble compound used as an insecticide. Formula: C 21 H 28 O 3

  2. Also called: pyrethrin II a compound of similar chemical structure and action, also found in pyrethrum. Formula: C 22 H 28 O 5

Origin of pyrethrin

C19: from pyrethrum + -in

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