1. a person or thing that traces something or by which something may be traced.
▪ a 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"
▪ a 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"
▪ a device which transmits a signal and so can be located when attached to a moving vehicle or other object.
