1. not considering the possible results of your actions; careless about how your actions might affect others
2. done without thinking or consideration

Examples

• It was thoughtless of him to park in the handicapped space.
• Her thoughtless comment hurt her friend’s feelings.
• The thoughtless driver cut in front of us without signaling.
• He made a thoughtless decision to quit his job without having another one lined up.
• She gave a thoughtless nod and continued reading her book.
• His thoughtless spending left him with no money for rent.
• The thoughtless remark slipped out before she could stop herself.