1. Taking insufficient care; negligent: a careless housekeeper; careless proofreading.
2. Marked by or resulting from lack of forethought or thoroughness: a careless mistake.
3. Showing a lack of consideration: a careless remark.
4. Unconcerned or indifferent; heedless: careless of the consequences.
5. Unstudied or effortless: danced with careless grace.
6. Exhibiting a disposition that is free from cares; cheerful: a careless grin; a careless wave of the hand.

SYNONYMS   careless, heedless, thoughtless, inadvertent. These adjectives apply to what is marked by insufficient care or attention. Careless often implies negligence: "It is natural for careless writers to run into faults they never think of" (George Berkeley). Heedless often suggests recklessness: "We have always known that heedless self-interest was bad morals; we know now that it is bad economics" (Franklin D. Roosevelt). Thoughtless applies to actions taken without due consideration: "But thoughtless follies laid him low / And stain'd his name" (Robert Burns). Inadvertent implies unintentional lack of care: With an inadvertent gesture, she swept the vase off the table.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.