coupler

Short definition from Wiktionary

Noun

1. 1
   Someone who couples things together, especially someone whose job it is to couple railway carriages.
2. 2
   Anything that serves to couple things together; but especially a device that couples railway carriages.
3. 3
   A device that connects two keyboards of an organ together so that they play together.
4. 4
   A device used to convert electronic information into audible sound signals for transmission over telephone lines.
5. 5
   An electrical device used to transfer energy from one electric device to another, especially without a physical connection.