tracer

noun

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

   noun.person

   Source: WordNet 3.0

2. an instrument used to make tracings

   noun.artifact

   Source: WordNet 3.0

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

   noun.artifact

   Source: WordNet 3.0

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

   noun.artifact

   Synonyms tracer bullet

   Source: WordNet 3.0

5. One who, or that which, traces.

   noun

   Source: webster1913

6. A person engaged (esp. in the express or railway service) in tracing, or searching out, missing articles, as packages or freight cars.

   noun

   Source: webster1913