the act of a person or thing that couples.

Machinery .

a device for joining two rotating shafts semipermanently at their ends so as to transmit torque from one to the other. Compare clutch 1 ( def. 12a ) .

a part with an inside thread for connecting two pipes of the same diameter.

a fitting at the end of a length of hose into which the end of another such length can be screwed or fitted.

Railroads . coupler ( def. 3 ) .

Electricity .

the association of two circuits or systems in such a way that power may be transferred from one to the other.

a device or expedient to ensure this.

a short length of plumbing pipe having each end threaded on the inside.

the part of the body between the tops of the shoulder blades and the tops of the hip joints in a dog, horse, etc.

linkage ( def. 5 ) .

noun

connection , junction , juncture , seam , union