adj. 25B6; adjective
he is unconcerned about their responses : INDIFFERENT, unmoved, apathetic, uninterested, incurious, dispassionate, heedless, unmindful; cool, lukewarm, unenthusiastic.
she tried to look unconcerned : UNTROUBLED, unworried, unruffled, insouciant, nonchalant, blasé, carefree, casual, relaxed, at ease, {cool, calm, and collected}; informal laid-back.
interested, anxious.