Thoughtless refers to the lack of consideration or attention towards others or towards the consequences of one's actions. It can imply carelessness, inconsiderateness, insensitivity or lack of forethought.

1. lacking in consideration for others; inconsiderate; tactless: a thoughtless remark. 2. not thinking enough; careless or heedless: thoughtless of his health. 3. devoid of or lacking capacity for thought. 4. characterized by or showing lack of thought. thought′less•ness, n.

From Longman Dictionary of Contemporary English thought‧less /ˈθɔːtləs $ ˈθɒːt-/ ●○○ adjective not thinking about the needs and feelings of other people, especially because you are thinking about what you want OPP thoughtful a selfish and thoughtless man it is thoughtless of somebody to do someth...