1. make (something) active or operative: "fumes from cooking are enough to activate the alarm"Similaroperateswitch onturn onstartstart offstart upset goingget goingtrigger offtriggertripset in motionactuateinitiateinitializeenergizeanimateOppositeswitch off
▪ convert (a substance, molecule, etc.) into a reactive form:"a DNA-repair enzyme that is activated by visible light"