insouciance
n. 无忧无虑；漫不经心；满不在乎
例句
She hid her worries behind an air of insouciance.
她掩饰着自己的烦恼，表现得无忧无虑。
《牛津词典》
He replied with characteristic insouciance: "So what?"
他用特有的漫不经心的口吻答道：“那又怎么样？”
《柯林斯英汉双解大词典》
The very direness of this possibility has produced a certain insouciance.
这种可能性的可怕已经产生了某种漠不关心。
