The word describes someone who is relaxed and calm in a way that shows that they do not care or are not worried about something. If someone is nonchalant about another person's pain or trouble, the word has a definite negative connotation.

A nonchalant person is someone who is not easily excited or upset. They remain calm and relaxed in most situations and don’t get frazzled easily. Nonchalant people are often described as “chill” or “laid back.”