tracer

noun

trac·​er ˈtrā-sər 

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

4

a

: 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 1d

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

New York City aims to hire 2,500 new employees as tracers; the state of Michigan instead plans to rely largely on volunteers. —Jeremy Konyndyk, Foreign Affairs, 8 June 2020

Each fiber is embedded with a unique molecular tracer during production, enabling genuine and transparent sharing of information about its lifecycle. —Sj Studio, Sourcing Journal, 4 Nov. 2024

The initial strikes were closely followed by a second wave, as video posted to social media by Tehran residents showed tracer fire and explosions illuminating the Iranian capital’s sky as dawn neared. —Helen Regan, CNN, 26 Oct. 2024

The test involves injecting a radioactive tracer into your body which helps identify whether cancer cells show up on the PET scan technology. —Susan Russell, Health, 12 Sep. 2024

Word History

First Known Use

14th century, in the meaning defined at sense 1

Kids Definition

tracer

noun

trac·​er ˈtrā-sər 

1

a

: a person who traces missing persons or property

b

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

2

a

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

b

: a substance and especially a labeled element or atom used to trace the course of a chemical or biological process

Medical Definition

tracer

noun

trac·​er ˈtrā-sər 

: 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