(a.) Without heed or care; inattentive; careless; thoughtless\; unobservant.

Lethean absentminded airy aloof amnestic apathetic arbitrary ataractic blase blind blocked bored capricious careless casual converted cursory deaf degage detached devil-may-care disinterested dispassionate disregardant disregardful distant distracted distrait easygoing feckless flippant forgetful forgetting free and easy grasshopper happy-go-lucky impassive improvident inadvertent inattentive inclined to forget inconsiderate incurious indifferent inexcitable inobservant insouciant lackadaisical lazy listless mindless neglectful negligent nonchalant oblivious offhand perfunctory phlegmatic pococurante reasonless reckless regardless repressed respectless shiftless stolid suppressed tactless thoughtless thriftless turned-off unaccommodating unanxious uncalculating uncaring uncomplaisant unconcerned uncooperative undiplomatic undiscriminating uneconomical unguarded unheedful unheeding unhelpful uninquiring uninterested uninvolved unmarking unmindful unnoticing unnoting unobliging unobservant unobserving unprepared unproviding unready unreasoning unreflecting unreflective unremarking unsolicitous untactful unthinking unthoughtful unthrifty withdrawn wrecking