Either of two liquid esters, C21H28O3 or C22H28O5, derived from chrysanthemums. It is the active ingredient of pyrethrum.

Pyr"eth*rin (?), n. [NL. Pyrethrum, generic name of feverfew, Gr. feverfew.] Chem.

A substance resembling, and isomeric with, ordinary camphor, and extracted from the essential oil of feverfew; -- called also Pyrethrum camphor.

<-- a complex of several substances. Used as insecticides. -->


© Webster 1913.

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