tracer

tracer
noun
  1. a person or thing that traces something or by which something may be traced, in particular
    追踪者,追踪装置,尤指
    ■a bullet or shell whose course is made visible in flight by a trail of flames or smoke, used to assist in aiming
    曳光弹
    ■a substance introduced into a biological organism or other system so that its subsequent distribution may be readily followed from its colour, fluorescence, radioactivity, or other distinctive property
    示踪剂,显光剂
    ■a device which transmits a signal and so can be located when attached to a moving vehicle or other object
    跟踪器(安装在移动车辆上或其他物体上,通过其发出的信号进行跟踪)
英语宝典
考试词汇表