tracer

Estimated CEFR level: C2 — Proficiency

Estimated from word frequency; not an official CEFR classification.

Definition

noun an investigator who is employed to find missing persons or missing goods
noun an instrument used to make tracings
noun (radiology) any radioactive isotope introduced into the body to study metabolism or other biological processes

From trace + -er.

"I got a tracer started after her." — Desert Conquest; or, Precious Waters, A. M. (Arthur Murray) Chisholm
I put everything I've got behind a tracer on that beam, but haven't been able to lift a single needle off the pin." — Triplanetary, E. E. (Edward Elmer) Smith
For two years he had contrived to elude the tracers, the killers, sent out by this creature, and now he had deliberately walked upon his swords. — Peter the Brazen: A Mystery Story of Modern China, George F. (George Frank) Worts

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