motionsensor
nounUK /ˈməʊʃn ˈsensə/
US /ˈmoʊʃn ˈsensər/
A motion sensor is a small device that notices when something moves.
The light turned on because the motion sensor felt someone walk by.
OTHER MEANINGS
2. A part of a security system that sets off an alarm when it detects movement.
The motion sensor triggered the alarm when the cat jumped on the sofa.
3. A device in automatic doors that makes them open when a person approaches.
The sliding doors opened smoothly thanks to the motion sensor above them.
4. A component in video game controllers that responds to the player's movements.
You can steer the car in the game by tilting the controller with its motion sensor.