Insouciant is the describing word for that same light not-worrying: an insouciant smile, an insouciant wave, an insouciant young man who walks into the exam as if it were nothing. The feeling is cheerful, or at least easy; the person is not chewing on the problem. Though actually, on the page it sits dangerously close to insolent, which means rude and disrespectful. Students mix the two because they look alike. Insouciant is light; insolent is sharp. One does not worry; the other does not respect. Like insouciance, it still feels a little French and a little literary. In speech, people more often say relaxed, chilled, or “she doesn’t care.” When they do use insouciant, they are usually painting a picture, not filling a form.

漫不經心的、滿不在乎的（別看成 insolent「無禮的」）