Synonym: indifference, unconcern. Similar words: nonchalant, balance, balanced, balance of, on balance, melancholy, carte blanche, glance. Meaning: ['nɑnʃəlɑns /'nɒnʃələns] 
n. the trait of remaining calm and seeming not to care; a casual lack of concern.
n. the trait of remaining calm and seeming not to care; a casual lack of concern. 
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1. He conceals his worries behind a mask of nonchalance.
2. Affecting nonchalance, I handed her two hundred dollar bills.
3. Beneath his apparent nonchalance he is as nervous and excited as the rest of us.
4. She shrugged, feigning nonchalance.
5. With epic nonchalance I motored north.
6. I think their nonchalance about not caring or not giving a damn about record sales is just not true.
7. She took her situation with much nonchalance.
8. She disguised her interest with nonchalance.
9. His nonchalant attitude nonchalance irritated me.
10. Some journalists criticize her nonchalance and indifference.
11. She showed a surprising nonchalance the first time she flew a plane.
12. But don't get too excited -- nonchalance doesn't mean nonstudying.
13. His nonchalance and aplomb in times of trouble always encouraged his followers.
14. 'Oh, by the way ...' she started, with a false air of nonchalance.
15. Rubbing the sweat from my brow,(sentencedict.com) I ask a few questions and smile with feigned nonchalance.
16. I tried to compose my features into a combination of nonchalance and justification.
17. How had he expected her to react to his betrayal - with laughter, perhaps, or nonchalance?
18. Then you wonder just how they can control the ball, the racquet and consequently the game with such nonchalance.
19. They loosen their ties and slouch against the wall with hands in pockets in manufactured nonchalance.
20. As for the promise to ban fox-hunting, it was given with such a blithe nonchalance as to be spine-chilling.
21. And from this detachment arise also his sense of freedom, his love of vagabondage and his pride and nonchalance.
22. Try not to convey arrogance, fear, resentment, conceit or too much nonchalance.
23. He stole the spotlight, one reporter wrote, "with the studied nonchalance of an old vaudeville trouper."
24. The impasse was made worse by Jobert's passionate nature, which masqueraded as cynical nonchalance.
25. He looks at her, lights a cigarette with elaborate nonchalance.
26. To mount the scaffolds . To advance to the muzzles of guns wit perfect nonchalance.
27. Mask He conceals his worries behind a mask of nonchalance.
28. She was very tense, but she preserved an appearance of nonchalance.
More similar words: nonchalant, balance, balanced, balance of, on balance, melancholy, carte blanche, glance, chance, parlance, by chance, petulance, ambulance, take a chance, surveillance, exhalation, catch-all, challenge, challenged, in charge, patriarchal, penchant, ranch, trial and error, trenchant, in charge of, branch, anchor, enchanting, once.