1. (a.) Not vigilant against danger; not wary or cautious; unguarded; precipitate; heedless; careless.

2. (a.) Unexpected; unforeseen; unaware.

artless asleep bluff blunt born yesterday brash brazen brazenfaced candid careless childlike confiding culpably negligent derelict direct foolhardy frank goofing off guileless hasty heedless hotheaded hubristic ill-advised improvident imprudent impudent inadvertent inattentive incautious inconsiderate indiscreet ingenu ingenuous injudicious innocent insolent laissez-faire lax loose mindless naive napping neglectful neglecting negligent nodding noninterfering nonrestrictive off-guard open openhearted outspoken overbold overcareless overconfident overly permissive oversure overweening permissive plain procrastinating rash reckless relaxed remiss scamping simple simplehearted simpleminded sincere single-hearted single-minded skimping slack sleeping slighting slurring temerarious thoughtless trustful trusting unadvised unalert uncautious unchary uncircumspect unguarded unprepared unready unreserved unrigorous unsophisticated unthinking unvigilant unwatchful unwise