| listen in(verb, expression, phrasal verb, study, consider) |
| mark(verb, consider, see, respect, note) |
| observer(noun, person, plant, watch, guard) |
| picket(noun, person, plant, watch, guard) |
| pipe(verb, mark, consider, see, respect) |
| rat(grass, sneak, decoy, informer, informant) |
| reconnoitre |
| remark(verb, mark, consider, see, respect) |
| scan(verb, consider, sound, see, respect) |
| shadow(noun, verb, follow, discover, watch) |
| sleeper(noun, person, plant, mole, infiltrator) |
| trail(verb, follow, discover, watch, pry) |
| turncoat(noun, grass, decoy, informer, rat) |
| watcher(noun, person, plant, watch, guard) |
| shit |
| be all ears(verb, study, consider, examine, review) |
| be watchful(verb, mind, notice, spot, avoid) |
| beam(verb, mark, consider, see, respect) |
| betray |
| bivouac(noun, warning) |