19 synonyms for nonchalant such as apathetic, airy, and and collected. Nonchalant is an adjective, and its antonyms are anxious and concerned.
Airy, and collected, apathetic, blasé, calm, casual, collected, composed, cool, cool as a cucumber, detached, dispassionate, indifferent, insouciant, laid-back, offhand, unconcerned, and unemotional.