1. An electronic component, such as a capacitor or resistor, that is incapable of amplification.

2. An artificial satellite that reflects an incoming signal without amplification.

3. A solar-power device that makes use of an existing structure to collect and utilize solar energy without the use of pumps, fans, etc.

4. A radar device that provides information for navigation, guidance, surveillance, etc., by receiving the microwave radiation. Such a passive device emits no microwave energy itself and therefore does not disclose its position.

5. A system that detects an object by the radiation that it emits, rather than by reflecting radiation off it, as in a passive infrared detector (PIR detector). Compare active device.