| analyst(agent, spy, informer, reporter, gumshoe) |
| audient |
| auditor |
| babbler(gossip, informer, tattle) |
| be all ears(bug, spy, monitor, poke, tap) |
| bird dog(expression, agent, spy, informer, reporter) |
| blab(gossip, informer, tattle) |
| bloodhound(agent, spy, informer, reporter, gumshoe) |
| bug(spy, monitor, poke, tap, eavesdrop) |
| bull(agent, spy, informer, reporter, gumshoe) |
| case(verb, examine, discover, watch, scrutinize) |
| catch sight of(verb, expression, idiom, examine, case) |
| circulator(gossip, informer, tattle, tattler, tattletale) |
| constable(noun, agent, spy, informer, reporter) |
| cop(noun, agent, spy, informer, reporter) |
| discover(verb, examine, watch, scrutinize, pry) |
| double agent(noun, expression, plant, agent, spy) |
| emissary(noun, plant, agent, operative, mole) |
| enquire |
| enquired |