Answer:
airy, aloof, apathetic, calm, careless, casual, collected, composed, cool, detached, disimpassioned, disinterested, dispassionate, easy, effortless, happy, impassive, imperturbable, incurious, indifferent, insouciant, lackadaisical, listless, loose, lukewarm, mellow, neglectful, negligent, neutral, placid, serene, trifling, uncaring, unconcerned, unemotional, unexcited, unfeeling, unflappable, unimpressible, unperturbed, unruffled, untroubled