When you're thoughtless about something, you don't spend much time thinking about what the consequences or effects on others might be. Smashing your neighbor's Jack-o-lantern was a thoughtless impulse you immediately regretted.

If you've ever said, "I didn't really think about it hurting someone's feelings—I just did it," you've acted in a thoughtless way. This adjective is always at least a little bit negative, basically the opposite of thoughtful. It's thoughtless to invite everyone except the new kid at school to your birthday party, and it's thoughtless to throw trash on the ground instead of in a trash can. It's always better to stop and think first!

Definitions of thoughtless

adj showing lack of careful thought

“the debate turned into thoughtless bickering”
lacking regard for the rights or feelings of others
inconsiderate, unconsidered
without proper consideration or reflection
unreflective, unthinking, unthoughtful
not exhibiting or characterized by careful thought
exhibiting or characterized by careful thought
showing concern for the rights and feelings of others
bemused, deep in thought, lost, preoccupied
deeply absorbed in thought
brooding, broody, contemplative, meditative, musing, pensive, pondering, reflective, ruminative
deeply or seriously thoughtful
given to cogitation
well thought out
resulting from careful thought
involved in or characterized by deliberation and discussion and examination
concerned with excogitating or having the power of excogitation
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adj without care or thought for others

“the thoughtless saying of a great princess on being informed that the people had no bread”
uncaring, unthinking
lacking regard for the rights or feelings of others

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