WordWeb Online

1. Marked by lack of attention or consideration or forethought or thoroughness; not careful
   "careless about her clothes"; "forgotten by some careless person"; "a careless housekeeper"; "careless proofreading"; "it was a careless mistake"; "hurt by a careless remark"
    
2. Effortless and unstudied
   "an impression of careless elegance"; "danced with careless grace"
    
3. (usually followed by 'of') without due thought or consideration
   "careless of the consequences"
   - regardless

See also: artless, carefulness, carelessly, carelessness, casual, cursory, haphazard, heedless, imprudent, inattentive, incautious, negligent, offhand, offhanded, passing, perfunctory, reckless, slapdash, slipshod, sloppy, superficial, unconcerned, unheeding

Antonym: careful

Encyclopedia: Careless