1. (

• tracer

) an investigator who is employed to find missing persons or missing goods ;

2. (

• tracer ,

) an instrument used to make tracings ;

3. (

• tracer ,

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

4. (

• tracer ,
• tracer_bullet

) ammunition whose flight can be observed by a trail of smoke ;