To actuate is to put into motion. The "act" in actuate can remind you of this word's meaning — to put into action. A lever might actuate a pump, or malice might actuate a crime.
Coming to us from the Latin word actus, which means "to act," actuate's meaning is simpler than it sounds — it just means to set in motion or activate some kind of motion. Think of one of those complex Rube Goldberg mouse traps; you know, the one where the boot kicks the ball that drops on the plank that tips over the ladder which rings a bell that cracks an egg that knocks over the cage onto the unsuspecting mouse. The boot actuates the whole shebang.