not paying enough attention to what one does

a careless typist.

not exact, accurate, or thorough

careless work.

done or said heedlessly or negligently; unconsidered

a careless remark.

not caring or troubling; having no care or concern; unconcerned (usually fol. by of, about, or in )

careless of the rights of others; careless about one's behavior; careless in speech.

possessed or caused without effort or art; unstudied

careless beauty.

Archaic . free from anxiety.

noun

care consideration , caution

noun

nonchalance , heedlessness , rashness , neglectfulness , neglect , negligence , disregard , haphazardness , inattention , sloppiness , thoughtlessness