| formal |
| guard |
| guarding(adjective, defensive) |
| hawk-eyed |
| hesitant(adjective, delicate, restrained, careful, safe) |
| hidden(cover, obscure, dark, secret, equivocal) |
| impregnable(adjective, secure, safe, snug, intact) |
| incredulous(wary, mistrustful, distrustful) |
| inhibited(cautious, restricted, suspicious, wary, orderly) |
| invulnerable(adjective, secure, perfect, safe, snug) |
| kept(adjective, reserved, retained) |
| obscured(cover, obscure, dark, secret, hidden) |
| offish(reserved, reticent, taciturn) |
| on the alert(expression, adjective, idiom, care, alert) |
| on the watch(expression, adjective, idiom, adverb, alert) |
| open-eyed(adjective, keen, anxious, alert, careful) |
| opposed(verb, defended) |
| precautious(adjective, careful, thoughtful, cautious, watchful) |
| precise(adjective, thoughtful, sober, cautious, prudent) |
| prepared(adjective, alert, careful, cautious, attentive) |