pyrethrin Syllabification: (py·re·thrin)Pronunciation: /pīˈrēTHrən, -ˈreTHrən/Definition of pyrethrin noun Chemistry any of a group of insecticidal compounds present in pyrethrum flowers. Origin: 1920s: from pyrethrum + -in1pyrethrin in other Oxford dictionaries Definition of pyrethrin in the British & World English dictionary
