Entry 1 sense Webster, 1913 Nonchalantly /nän'-shəl-än'-tlē/ · Non·cha·lant·ly · IPA /nˈɑnʃəlˈɑntliː/ 01 adv. In a nonchalant, indifferent, or careless manner; coolly. 1. In a nonchalant, indifferent, or careless manner; coolly.