casualness
n. 偶然；漫不经心；随便
例句
He was sure that the casualness of the gesture was deliberate.
他确信那似乎漫不经心的姿态是有意装出来的。
《牛津词典》
She introduced herself with studied casualness.
她故作轻松地做了自我介绍。
T-shirts, the epitome of American casualness, have moved upmarket.
T恤，美国人的随意的标志，已提升至高档商品之列。
《柯林斯英汉双解大词典》
