(automotive) A vehicle transmission which shifts gears automatically in response to vehicle speed and/or load, and does not require any driver input to manually change gears under normal driving conditions; an automatic gearbox.

plural of automatic transmission

(automotive) A multi-speed motor vehicle transmission where part of its operation is automated (typically the clutch actuation; partially automated) but the driver's input is still required to manually operate a gearshift and to change gear by hand/foot; i.e., not fully-automatic. Names for specific types of semi-automatic transmissions include clutchless manual, auto-manual, auto-clutch manual, and paddle-shift transmissions. These systems facilitate gear changes for the driver by operating the clutch system automatically, usually by means, or under control of an actuator or servo, sensors, a solenoid, and an integrated electronic control module, while still requiring the driver's input to manually shift gears.