motion detector
noun1
A device used in security systems that can alert the user of the presence of a moving object.
- Higman and his sidekick, a geophysical engineering student named Krishna Divakarla from the Colorado School of Mines, are the volunteer cavalry. They are planting homemade motion detectors on the quivering slopes.2026 February 27, Paul Salopek, “Hazard Cascade”, in National Geographic: