n. 25B6; noun SPY, (secret) agent, plant, intruder, interloper, subversive, informant, informer, mole, entrist, entryist; N. Amer. informal spook.
INFILTRATOR
Meaning of INFILTRATOR in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012