- noun a substance which is used to kill insects
- a natural or synthetic substance that kills insects. In agriculture most pesticides are either chlorinated hydrocarbons, organophosphorous compounds or carbamate compounds, although some are produced from plant extracts. Insecticides are used in a number of ways, including spraying and dusting, or in granular forms as seed dressings. In the form of a gas, insecticides are used to fumigate greenhouses and granaries.