- coupler (sense )
- a bar at the rear of a tractor for attaching a plow, harrow, etc.
- A bar across the rear of a tractor for hitching machinery.
- A railroad coupler.
- (rail transport) An open-mouthed bar at the end of a car, which receives a coupling link and pin by which the car is drawn. It is usually provided with a spring to give elasticity to the connection between the cars of a train.
- (rail transport) A bar of iron with an eye at each end, or a heavy link, for coupling a locomotive to a tender or car.
- (road transport) A device to couple a powered road vehicle to a load to transfer tractive effort to the load, either as a push or as a pull. (See also Drawbar)
- (music) A sliding bar on a Hammond organ, controlling the volume of a waveform.
- (engineering) A device for changing the tools on milling machines