The Collaborative International Dictionary of English v.0.48:
Coupling \Coup"ling\ (-l?ng), n.
1. The act of bringing or coming together; connection; sexual
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
Coupling pin, a pin or bolt used in coupling or joining
together railroad cars, etc.