| spy(noun, verb, person, information, follow) |
| snoop(noun, verb, person, plant, examine) |
| detective(noun, information, plant, watch, investigate) |
| gumshoe(noun, slang, investigate, agent, spy) |
| investigator(noun, person, plant, investigate, agent) |
| dick(noun, slang, investigate, agent, spy) |
| private eye(noun, expression, agent, spy, informer) |
| eye(noun, informal, investigate, agent, spy) |
| private detective(noun, expression, idiom, private, detective) |
| shamus(noun, agent, spy, informer, reporter) |
| sleuthhound(noun, detective) |
| stag(verb, examine, case, discover, watch) |
| eavesdropper(noun, information, agent, spy, scout) |
| operative(noun, plant, agent, mole, gumshoe) |
| private investigator(noun, expression, agent, spy, informer) |
| scout(noun, verb, person, plant, examine) |
| tail(noun, verb, examine, case, discover) |
| tec |
| Hawkshaw |
| P.I.(noun, detective) |