from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Lack of interest; indifference.
- n. Lack of worry or apprehensiveness.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. indifference or lack of concern.
from the GNU version of the Collaborative International Dictionary of English
- n. Want of concern; absence of anxiety; freedom from solicitude; indifference.
from The Century Dictionary and Cyclopedia
- n. Want of concern; absence of anxiety; freedom from solicitude; indifferentism; indifference; apathy.
- n. Synonyms Indifference, Insensibility, etc. See apathy.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a feeling of lack of concern
- n. the trait of remaining calm and seeming not to care; a casual lack of concern
Probably back-formation from unconcerned.(American Heritage® Dictionary of the English Language, Fourth Edition)