/ ˈkeələs; NAmE ˈkerləs/ adjective
1.
not giving enough attention and thought to what you are doing, so that you make mistakes :
It was careless of me to leave the door open.
Don't be so careless about / with spelling.
a careless worker / driver
OPP careful
2.
resulting from a lack of attention and thought :
a careless mistake / error
3.
careless of sth ( formal ) not at all worried about sth :
He seemed careless of his own safety.
4.
not showing interest or effort
SYN casual :
She gave a careless shrug.
a careless laugh / smile
► care·less·ly adverb :
Someone had carelessly left a window open.
She threw her coat carelessly onto the chair.
'I don't mind,' he said carelessly.
► care·less·ness noun [ U ]:
a moment of carelessness
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WORD ORIGIN
Old English carlēas free from care (see care , -less ).