Coup·ling n.
 1. The act of bringing or coming together; connection; sexual union.
 2. Mach. 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 coupling shaped like a journal box, for clamping together the ends of two shafts, so that they may revolve together.
 Coupling pin, a pin or bolt used in coupling or joining together railroad cars, etc.

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