(a)carelessmarked 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”
(s)careless, regardless(usually followed by `of') without due thought or consideration“careless of the consequences”, “crushing the blooms with regardless tread”