adj. 25B6; adjective
an unguarded frontier : UNDEFENDED, unprotected, unfortified; vulnerable, insecure, open to attack.
an unguarded remark : CARELESS, ill-considered, incautious, thoughtless, rash, foolhardy, foolish, indiscreet, imprudent, injudicious, ill-judged, insensitive; poetic/literary temerarious.
an unguarded moment : UNWARY, inattentive, off guard, distracted, absent-minded.