Coupler n. One who couples; that which couples, as a link, ring, or shackle, to connect cars.
Coupler of an organ, a contrivance by which any two or more of the ranks of keys, or keys and pedals, are connected so as to act together when the organ is played.
... men went out and she was left alone. A flagman, hat in hand, passed through the car. The shock of the engine coupler striking the buffer hardly disturbed her reverie; for her the ... — The Daughter of a Magnate • Frank H. Spearman