Unconcerned, a.
Not concerned; not anxious or solicitous; easy in mind; carelessly secure; indifferent; as, to be unconcerned at what has happened; to be unconcerned about the future. -- Un`con*cern"ed*ly, adv. -- Un`con*cern"ed*ness, n. Happy mortals, unconcerned for more. Dryden.
Shades of meaning
Fernald lists unconcerned only as an antonym, under eager, inquisitive.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given