careless

Concise Oxford English Dictionary © 2008 Oxford University Press:
careless/ˈkeələs/

▶adjective

• 1 not giving sufficient attention or thought to avoiding harm or mistakes.

• 2 (careless of/about) not concerned or worried about.

  ■ showing no interest or effort; casual.

– derivatives
carelessly adverb,
carelessness noun.

– origin OE carlēas ‘free from care’ (see care, -less).