THESAURUS
off guard
asleep, culpably negligent, derelict, goofing off, inadvertent, inattentive, incautious, laissez-faire, lax, loose, napping, neglectful, neglecting, negligent, nodding, noninterfering, nonrestrictive, overly permissive, permissive, procrastinating, relaxed, remiss, scamping, skimping, slack, sleeping, slighting, slurring, unalert, uncautious, uncircumspect, unguarded, unprepared, unready, unrigorous, unvigilant, unwary, unwatchful