tracers

/T R EY1 S ER0 Z/
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.

Source: https://en.wiktionary.org/wiki/tracer, https://en.wiktionary.org/wiki/tracers