She watched his progress towards the pavilion, saw him now responding condescendingly to an ingratiating bow, now exchanging friendly, nonchalant greetings with his equals, now assiduously trying to catch the eye of some great one of this world, and taking off his big round hat that squeezed the tips of his ears.
There are no more uses of "nonchalant" in the book.
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I could tell she was nervous, but she was trying to look nonchalant.
How could she be so nonchalant about making him suffer?