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

Cool tech, but so much worse than the camera from behind with normal shot tracer... —Savannah Leigh Richardson, MSNBC Newsweek, 6 June 2025

Pollen is a biological marker and geographic tracer of this ancient change. —Francisca Oboh Ikuenobe, The Conversation, 20 May 2025

Ball also said the tracer fire – ammunition containing a pyrotechnic charge illuminating its trajectory – seen in the GHF’s footage is consistent with the use of machine guns. —Jeremy Diamond, CNN Money, 4 June 2025

But this lower end of the galactic scale is still rather murky, in part because the stars that serve as observable tracers of small galaxies can form even smaller structures called star clusters. —Phil Plait, Scientific American, 8 May 2025

Word History

First Known Use

14th century, in the meaning defined at sense 1

Rhymes for tracer

• acer
• baser
• chaser
• pacer
• racer
• spacer
• eraser
• replacer
• radiotracer

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