stool-pigeon

n (infml 口) person who acts as a decoy, esp to trap a criminal 诱人上圈套者; （尤指）用以诱捕罪犯的人.

stomach-pump, stomp, stone, stone head, stone-cold, stone-dead, stone-deaf, stone-fruit, stoneless, stonemason, stonewall, stonewaller, stonewalling, stoneware, stonework, stonily, stony, stood, stooge, stool, stoop, stop, stop by, stop off, stop press, stop short, stop to do sth., stop-go, stop-light, stop-press, stop-watch, stop...from, stopcock, stopgap, stopover, stoppage, stopper, stopping, stopping train, stopwatch,