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.