coupling

noun

1. the act of joining together, pairing, copulating, etc.
2. a flexible or rigid mechanical device or part for joining parts together, as two shafts
3. coupler (sense )
4. the part of the body, as of a dog or horse, between the hipbones and the ribs; loin
5. a method or device for joining two electric circuits for the transference of energy from one to the other