The term 'SHIP'S STEERING DEVICE' can be summarized as a RUDDER, which is a 6-letter word. A RUDDER is a flat piece of material attached to the stern of a boat or ship that is used to steer the vessel. It is usually controlled by a wheel or tiller and is moved left or right to change the direction of the boat. The RUDDER is an important part of a ship's navigation system and is essential for safe and efficient operation.