[ trey-ser ]


  1. a person or thing that traces. trace.
  2. a person whose business or work is the tracing tracing trace of missing property, parcels, persons, etc.
  3. an inquiry sent from point to point to trace a missing shipment, parcel, or the like, as in a transportation system.
  4. any of various devices for tracing tracing trace drawings, plans, etc.
  5. Also called tracer ammunition. ammunition containing a chemical substance that causes a projectile to trail smoke or fire so as to make its path visible and indicate a target to other firers, especially at night.
  6. the chemical substance contained in such ammunition.
  7. a substance, especially a radioactive one, traced trace through a biological, chemical, or physical system in order to study the system.


/ ˈtreɪsə /


  1. a person or thing that traces
    1. a projectile that can be observed when in flight by the burning of chemical substances in its base
    2. ammunition consisting of such projectiles
    3. ( as modifier )

      tracer fire

  2. med any radioactive isotope introduced into the body to study metabolic processes, absorption, etc, by following its progress through the body with a gamma camera or other detector
  3. an investigation to trace missing cargo, mail, etc


/ trāsər /

  1. An identifiable substance, such as a dye or radioactive isotope, that can be followed through the course of a mechanical, chemical, or biological process. Tracers are used in radioimmunoassays and other laboratory testing. The use of radioactive iodine, for example, can give information about thyroid gland metabolism.
  2. Also called label

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Word History and Origins

Origin of tracer1

First recorded in 1535–45; trace 1 + -er 1
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Example Sentences

Contact tracers tried to identify everyone exposed and figure out where the virus might have come from.

From Vox

If somebody tests positive for covid-19, contact tracers use it to track down those who got close enough to be potentially infected.

America’s pandemic response has suffered from a well-publicized lack of PPE, of tests, of contact tracers.

From Fortune

Spotting the novel virus as early as possible can signal infectious people to isolate themselves, and help contact tracers identify and notify anyone they’ve been in close quarters with.

Contact tracers in Anne Arundel County reached out to families every day to check on possible symptoms.

Suddenly, the darkness came alive with muzzle flashes and tracer rounds.

First, however, I was injected with a radioactive tracer that allowed activity in my brain to show up on the scan.

Tracer bullets, each with a descending arc, were zinging all around as Rigg swung LCI(L)-88 to the right.

Below us, on Sultan Ismail Street, government troops thrust lances of tracer fire towards a horde of approaching cadavers.

Three men snapped down behind the tracer-guns, firing without aiming, in a frenzied attempt to catch the fleeing sled.

Firing was incessant from the beginning, and the air seemed blue with tracer smoke.

Here I am, a mechanical engineer, about to tackle the job of a professional detective and tracer of missing persons.

A thin stream of glowing red and orange tracer bullets soared up at the plane from the Catanzas side of the bay.

Every tenth bullet was a tracer that made a white trail in the sky allowing you to track them.





tracelesstracer bullet