| observing(adjective, careful, cautious, aware, attentive) |
| on guard(expression, adjective, sharp, bright, lively) |
| on lookout(expression, cautious, tactful, circumspect) |
| on the QT(expression, idiom, mysterious, reticent, taciturn) |
| on the inside(expression, sharp, smart, intelligent, clever) |
| on the qui vive(expression, idiom, sharp, bright, lively) |
| on to(expression, careful, aware, attentive, wary) |
| on top of(expression, sharp, smart, intelligent, clever) |
| penetrating(sharp, smart, intelligent, clever, astute) |
| piercing(sharp, smart, intelligent, clever, astute) |
| playing it cool(expression, careful, thoughtful, prudent, watchful) |
| playing safe(expression, careful, thoughtful, prudent, watchful) |
| plugged in(expression, careful, cautious, aware, attentive) |
| precautious(careful, thoughtful, cautious, watchful, tactful) |
| prevaricating |
| probing(sharp, smart, intelligent, clever, astute) |
| profound(sharp, smart, intelligent, clever, astute) |
| provident(careful, thoughtful, cautious, prudent, suspicious) |
| psyched up(expression, sharp, bright, lively, active) |
| pussyfoot(careful, thoughtful, prudent, watchful, guarded) |