tracer

noun

1. an investigator who is employed to find missing persons or missing goods

Definition categories: person, detective, investigator

2. an instrument used to make tracings

Definition categories: man–made, instrument

3. (radiology) any radioactive isotope introduced into the body to study metabolism or other biological processes

Definition categories: man–made, radioisotope

4. ammunition whose flight can be observed by a trail of smoke

Definition categories: man–made, ammo, ammunition