'Unconcern' definitions:

Definition of 'unconcern'

From: WordNet
noun
The trait of remaining calm and seeming not to care; a casual lack of concern [syn: nonchalance, unconcern, indifference]
noun
A feeling of lack of concern [ant: concern]

Definition of 'Unconcern'

From: GCIDE
  • Unconcern \Un`con*cern"\, n. Want of concern; absence of anxiety; freedom from solicitude; indifference. [1913 Webster]
  • A listless unconcern, Cold, and averting from our neighbor's good. --Thomson. [1913 Webster]

Synonyms of 'unconcern'

From: Moby Thesaurus