A favorite with children for over fifty years, experience the excitement with the four orphaned Alden children as they roam the countryside finding new mysteries to solve.
antonym - a word that expresses a meaning opposed to the meaning of another word, in which case the two words are antonyms of each other; to him the antonym of `gay' was `depressed'. opposite, opposite word.
An antonym is a word that is the opposite in meaning of another word, so it makes sense that the opposite of careful, or being full of care, is a word that means not paying close attention, or expressing little to no care.