pyrethrin

1. (organic chemistry) Any of a number of naturally occurring insecticides extracted from the pyrethrum plant; unusual in having a cyclopropane ring.Examples: "Ecoparasite control, with appropriate concentrations of carbaryl, malathion, or pyrethrin dusts, is permissible if the agent is applied externally to both test and control animals not less than seven days prior to the start of the test."; "The biggest risk raised in the findings, Mr. Abecassis said, is the exposure to pesticides, which have been linked to a range of serious illnesses including fatal cancers and organ damage. Six of the tested products contained chemicals like myclobutanil and pyrethrins in concentrations far above state limits, according to the analysis."