insouciance (n.)

• abandon
• acedia
• aloofness
• apathy
• ataraxia
• blah
• blahs
• boredom
• carelessness
• casualness
• comatoseness
• detachment
• disinterest
• disinterestedness
• dispassion
• disregard
• dullness
• easiness
• easygoingness
• forgetfulness
• hastiness
• heartlessness
• hebetude
• heedlessness
• hopelessness
• impassiveness
• impassivity
• inattention
• inconsiderateness
• inconsideration
• indifference
• lassitude
• laziness
• lethargy
• listlessness
• mindlessness
• negligence
• nonchalance
• numbness
• oblivion
• passiveness
• passivity
• phlegm
• recklessness
• resignation
• sloth
• sluggishness
• sopor
• spiritlessness
• stolidity
• stupefaction
• stupor
• tactlessness
• thoughtlessness
• torpidity
• torpidness
• torpor
• unconcern
• unmindfulness
• withdrawal
• withdrawnness