nonchalant

 
Pronunciation: /ˈnɒnʃ(ə)l(ə)nt/

adjective

  • (of a person or manner) feeling or appearing casually calm and relaxed; not displaying anxiety, interest, or enthusiasm: she gave a nonchalant shrug

Derivatives

nonchalantly

adverb

Origin:

mid 18th century: from French, literally 'not being concerned', from the verb nonchaloir