railway turntable
A rotating platform used to turn locomotives or rolling stock in a rail yard or roundhouse.
The steam locomotive was turned around on the railway turntable.
car turntable; driveway turntable
A rotating platform for turning vehicles in tight spaces, such as a garage or driveway.
They installed a car turntable in the narrow parking lot to make it easier to turn the vehicle around.
Compound of 転 (turn) + 車 (vehicle) + 台 (platform). The exact historical derivation is uncertain, but the kanji directly reflect the function.