MDBG Mobile Chinese English Dictionary (iPhone, Android, Windows Phone)

上线	shàng xiàn	to go online; to put sth online / to reach a specific standard / to put into production / handler (person who oversees and directs the activities of another person in a gang, spy ring etc)
底线	dǐ xiàn	bottom line; the limit of what one is prepared to accept / (sports) baseline / (sewing) under thread / spy; informer; plant
侦察兵	zhēn chá bīng	a scout / spy
窥视	kuī shì	to peep at / to spy on / to peek
侦察员	zhēn chá yuán	detective / investigator / scout / spy
间谍	jiàn dié	spy
探子	tàn zi	intelligence gatherer / spy / detective / scout / sound (medical instrument) / long and narrow probing and sampling utensil
刺探	cì tàn	to pry into / to spy on / to probe into
侦察机	zhēn chá jī	surveillance aircraft / spy plane
敌探	dí tàn	enemy spy
暗中监视	àn zhōng jiān shì	to monitor secretly / to spy on
奸细	jiān xi	a spy / a crafty person
细作	xì zuò	(old) spy; secret agent
谍报	dié bào	spy report / intelligence
间谍活动	jiàn dié huó dòng	espionage / spying
线人	xiàn rén	spy / informer
间谍网	jiàn dié wǎng	spy network
窥伺	kuī sì	to spy upon / to lie in wait for (an opportunity)
特务	tè wu	special assignment (military) / special agent / operative / spy
内鬼	nèi guǐ	mole / spy / rat / traitor