tracer

noun

1. 1

   A compound, element, or isotope used to track the progress or history of a natural process.

2. 2

   A round of ammunition for a firearm that contains magnesium or another flammable substance arranged such that it will burn and produce a visible trail when fired in the dark.

3. 3

   The act or state of tracking or investigating something.

4. 4

   A request to trace the movements of a person or an object, such as a shipment.

5. 5

   A person who traces something.

6. 6

   A device or instrument used to assist in making tracings.