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.
COUPLING n. 2 definitions
A device or contrivance which serves to couple or connect adjacent parts or objects; as, a belt coupling, which connects the ends of a belt; a car coupling, which connects the cars in a train; a shaft coupling, which connects the ends of shafts. Box coupling, Chain coupling. See under Box, Chain. -- Coupling box, a co…