1. bullets or shells containing a pyrotechnic composition that burns during flight to make the projectile's path visible
Usage: military
2. people who trace or track something, especially missing persons or objects
3. radioactive isotopes used to follow the path of a substance through a biological or chemical system
Usage: scientific

Examples

• The soldiers could see the enemy position clearly thanks to the bright tracers streaking through the night sky.
• Tracer rounds helped the gunner adjust his aim during the firefight.
• The insurance company hired tracers to locate the stolen vehicles.
• Professional tracers specialize in finding people who have disappeared.
• Scientists injected radioactive tracers to monitor blood flow through the patient's heart.
• The researchers used tracers to study how nutrients move through the ecosystem.
• Medical tracers allow doctors to see how organs function in real time.