Definition of tracer in English:

tracer

Line breaks: tracer
Pronunciation: /ˈtreɪsə
 
/

noun

1A person or thing that traces something or by which something may be traced, in particular:
1.1A bullet or shell whose course is made visible in flight by a trail of flames or smoke, used to assist in aiming: the night sky turned into a light show of artillery, flares, and tracers [mass noun]: the night was lit up by tracer [as modifier]: tracer fire
More example sentences
  • Then, of course, all the tracer fire started coming in, and we were really in trouble.
  • On top of this, other final elements were and filmed separately and then digitally added to the shot to replicate tracer fire, smoke, and shell casings falling from the machine guns.
  • The origin of the bullets and tracers - the gun flashes - were almost at eye level when Rick and I looked back inside the cockpit at the altimeter.
1.2A substance introduced into a biological organism or other system so that its subsequent distribution may be readily followed from its colour, radioactivity, or other distinctive property: they used radioactive carbon as a tracer [mass noun]: transfer of tracer from spinal fluid to blood
More example sentences
  • So they enrolled him in a study, testing a new imaging system that would allow them to follow a radioactive tracer through his brain to see the plaque that has built up around the nerve cells.
  • It relies on the difference in distribution of a radioactive tracer, such as thallium, at rest and after stress.
  • A bone scan falls under the category of nuclear medicine, which means that it uses tiny amounts of radioactive materials called tracers (radionuclides).
1.3A device which transmits a signal and so can be located when attached to a moving vehicle or other object.
More example sentences
  • And you'll be happy to know we knew exactly where you were, we installed tracers into all the vehicles.
  • The tracer was attached and they continued their pursuit.

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