Entry 1 sense Webster, 1913 Insecticide /ĭnˌ-sĕk'-təs-īdˌ/ · In·sec·ti·cide · IPA /ɪnˈsɛk.təˌsaɪd/ 01 n. An agent or preparation for destroying insects; an insect powder or spray. 1. An agent or preparation for destroying insects; an insect powder or spray.