movement sensor
nounUK /ˈmuːvmənt ˈsɛnsə/
US /ˈmuːvmənt ˈsɛnsər/
A movement sensor is a small device that notices when something moves.
The light turned on because the movement sensor felt someone walk by.
OTHER MEANINGS
2. A part in a game console that senses when you move your body.
The movement sensor in the controller made the game character jump.
3. A gadget on a door that turns on a light when someone comes near.
The movement sensor by the door switched on the porch light.
4. A device in a robot that helps it know when things around it move.
The robot stopped when its movement sensor spotted a cat.