| espionage agent(noun, expression, plant, agent, operative) |
| espy |
| examine(verb, discover, look, watch, search) |
| eye(noun, verb, look, agent, scrutinize) |
| eyeball(verb, examine, case, discover, look) |
| fed(agent, spy, informer, reporter, gumshoe) |
| ferret(noun, person, spy, sneak, vacationist) |
| ferret about(verb, expression, phrasal verb) |
| ferreting |
| filch |
| fink(agent, spy, gossip, nuisance, informer) |
| fish out(verb, expression, examine, case, discover) |
| flatfoot(agent, spy, informer, reporter, gumshoe) |
| flibbertigibbet(gossip, informer, tattle, tattler, tattletale) |
| fly on the wall(noun, view) |
| fool with |
| foreign agent(noun, expression, plant, agent, operative) |
| fussbudget(gossip, nuisance, ferret, nosy, vacationist) |
| gape(verb, look, scan, scrutinize, bug) |
| gaze(verb, look, scan, scrutinize, bug) |