insecticide, insecticides 1. One who or that which kills insects, an insect-killer; specifically, a preparation used for destroying insects. 2. The killing of insects. An insecticide is a pesticide used to kill insects in all developmental forms. They include ovicides and larvicides used against the eggs and larvae of insects. Insecticides are wid... Found on http://www.wordinfo.info/words/index/info/view_unit/1072/