tracer

n 1 person or thing that traces 追踪者; 追踪装置; 描摹者; 描摹工具. 2 bullet or shell whose course is made visible by a line of smoke, etc left behind it 曳光弹: [attrib 作定语] tracer bullets 曳光弹. 3 radioactive substance whose course through the human body, etc can be traced by the radiation it produces, used for investigating a chemical or biological process 示踪物.

town house, town planning, town-folk, townee, townsfolk, `townspeople, township, townsman, toxaemia (also toxemia), toxic, toxicity, toxicologist, toxicology, toxin, toy, toy animal, Toyota, toyshop, trace, trace element, traceable, tracery, trachea, tracheotomy, trachoma, tracing, tracing-paper, track, track and field, track down, track events, track out, track record, track suit, tracked, tracking station, tract, tractability, tractable, traction, traction-engine,