A stick shaker
is a mechanical device connected to the controls of an airliner
(also other types of aircraft such as bizjets) in order to warn the pilots that they are close to stalling the aircraft. In larger aircraft a stall is often impossible to recover from, so the stick shaker will eventually pull the controls right out of the pilot's hands to push the nose down, if need be. In the latter case the device is often referred to as a "kicker" or "stick-pusher", although it is often the same device internally.