thoughtlessness

/ˈθɔtləsnəs/
noun
  1. The quality or state of being inconsiderate of others.
    • His thoughtlessness was evident when he forgot his friend's birthday entirely.
    • She apologized for her thoughtlessness in not inviting everyone to the party.
    • The thoughtlessness of leaving the gate open allowed the dog to escape.
  2. The quality of acting without careful thought or judgment.
    • Her thoughtlessness with money led to serious debt problems.
    • Thoughtlessness in the lab can result in dangerous chemical spills.
    • The accident was caused by a moment of thoughtlessness on the driver's part.