| plant(noun, person, informal, source, grass) |
| spook(noun, person, plant, informal, investigate) |
| stare(verb, consider, see, note, regard) |
| witness(verb, mark, consider, see, respect) |
| betrayer(noun, opposition, source, agent, villain) |
| bug(verb, study, consider, examine, review) |
| espionage agent(noun, expression, person, plant, mole) |
| gaze(verb, mark, consider, see, respect) |
| get a load of(verb, expression, idiom, phrasal verb, mark) |
| inspect(verb, study, mark, consider, see) |
| make out(verb, expression, phrasal verb, mark, consider) |
| mole(noun, person, plant, watch, warning) |
| peep(verb, consider, see, note, regard) |
| recognize(verb, mark, see, note, regard) |
| reconnoiter(verb, study, consider, follow, examine) |
| snitch(grass, sneak, decoy, informer, rat) |
| stool pigeon(noun, expression, idiom, grass, sneak) |
| take in(verb, expression, phrasal verb, mark, consider) |
| eavesdropper(noun, information, agent, sneak, informer) |
| emissary(noun, person, plant, watch, representative) |