Source : Webster's Revised Unabridged Dictionary (1913)

Insecticide \In*sec"ti*cide\, n. [Insect + L. caedere to kill.]
   An agent or preparation for destroying insects; an insect
   powder. -- {In*sec"ti*ci`dal}, a.

Source : WordNet®

insecticide
     n : a chemical used to kill insects [syn: {insect powder}]