thoughtlessness

adjective

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

adjective

1. inconsideratea thoughtless remark
2. having or showing lack of thoughta thoughtless essay
3. unable to think; not having the power of thought

adj.“inconsiderate,” 1794, from thought + -less. Related: Thoughtlessly; thoughtlessness.