The Oxford Thesaurus An A-Z Dictionary of Synonyms - unguarded adj.

1) incautious, unwary, careless, inattentive, heedless, inobservant, inadvertent, unthinking, unwatchful, unvigilant: He let the intruder past him in an unguarded moment. 2) defenceless, unprotected, undefended, unfortified, open, uncovered, exposed, vulnerable: The sentry insisted that he had left his post unguarded for only a few minutes. 3) indiscreet, careless, imprudent, unwise, hasty, unthinking, thoughtless; guileless, incautious: He was anxious to restore good relations after his unguarded remarks about their associates.