trac·er | \ˈtrā-sər \

Definition of tracer 

1 : one that traces, tracks down, or searches out: such as

a : a person who traces missing persons or property and especially goods lost in transit

b : an inquiry sent out in tracing a shipment lost in transit

2 : one who traces designs, patterns, or markings

3 : a device (such as a stylus) used in tracing

4a : ammunition containing a chemical composition to mark the flight of projectiles by a trail of smoke or light

b : a substance used to trace the course of a chemical or biological process especially : label sense 3d

Examples of tracer in a Sentence

The enemy fired tracers at the aircraft carrier. They injected her with a radioactive tracer and tracked it via X-rays.

Recent Examples on the Web

Typically, a chemical tracer would be added to the water, like a salt or dye, to track the flow. Kevin Davenport, idahostatesman, "Yellowstone's magma chamber is more powerful than we knew. Here's why studying it matters.," 3 July 2018 The radioactive tracer lights up on a computer monitor wherever the heart's blood vessels are blocked or bones are riddled with potentially cancerous tumors. Sarah Varney, Washington Post, "In Wisconsin, Hopes Rise For Production Of A Lifesaving Radioactive Isotope," 16 Jan. 2018 The wildfire was supposedly started by tracer rounds fired at a shooting range. Doyle Rice, USA TODAY, "Western wildfires: Thousands flee from dozens of blazes, including Colorado's 3rd-biggest on record," 5 July 2018 To trace how the cells and their progeny changed over time, the researchers equipped some of the single-cell fish embryos with genetic tracers: many tiny pieces of unique DNA, injected into the embryos' cytoplasm. Elizabeth Pennisi, Science | AAAS, "How one cell gives rise to an entire body," 26 Apr. 2018 Antiaircraft tracers lit up the skies over Damascus and explosive sounds bounced off the city’s hills, mixing with the mosques’ calls to prayer. Raja Abdulrahim, WSJ, "A Divided Syria Reacts Wearily to Airstrikes From the U.S. and Its Allies," 14 Apr. 2018 The official said investigators searching Paddock's hotel room found tracer rounds and a document with the name of the Mesa man who sold him the ammunition. Matt Pearce,, "Warrants in Las Vegas mass shooting reveal name of additional 'person of interest'," 31 Jan. 2018 Geologists placed tracer dyes in the underground rivers and learned the cavern aquifer extends 4 miles east to White Oak Sinks, in the isolated valley of Cades Cove in Great Smoky Mountains National Park near the North Carolina line. John Bordsen, USA TODAY, "North Korean nukes tracked from Tennessee tourist caverns," 13 Apr. 2018 The 351-foot tracer cut the lead to 7-4, chased reliever Andrew Chafin from the mound and gave Myers his fifth career multi-homer performance. Dennis Lin,, "Myers, Padres rally from six-run deficit to stun Diamondbacks," 10 Sep. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'tracer.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of tracer

14th century, in the meaning defined at sense 1

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The first known use of tracer was in the 14th century

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English Language Learners Definition of tracer

: a type of bullet that shows its path by creating smoke or light as it moves through the air

medical : a substance that is put in a patient's body so that doctors can watch a biological process (such as digestion) or see how a condition (such as cancer) is progressing


trac·er | \ˈtrā-sər \

Medical Definition of tracer 

: a substance used to trace the course of a process specifically : a labeled element or atom that can be traced throughout chemical or biological processes by its radioactivity or its unusual isotopic mass

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