a.
1.
Unperplexed, undisturbed, untroubled, free from care, without anxiety, unsolicitous.
2.
Heedless, thoughtless, inattentive, unconcerned, unmindful, incautious, unthinking, forgetful, remiss, listless, supine, regardless, neglectful, negligent.
3.
Unconsidered, inconsiderate.