Casually unconcerned or indifferent. See Synonyms at cool.
[French, from Old French, present participle of nonchaloir, to be unconcerned : non-, non- + chaloir, to cause concern to (from Latin calēre, to be warm, heat up; see kelə-1 in the Appendix of Indo-European roots).]
non′cha·lance (-läns) n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.