Thoughtlessly means doing or saying things without thinking about how they might affect others. It's like acting on impulse.
When people talk about someone behaving thoughtlessly, they often mean that this person isn't considering other people's feelings or needs when making decisions or taking actions. For example, if you spill coffee on your friend's new shirt because you weren't careful and didn't think about what could happen, people might say you did it thoughtlessly. It doesn't have to be something big; even small things, like not saying "excuse me" before interrupting someone in conversation, can show thoughtlessness.
showing thoughtlessness
Example: he treated his parents thoughtlessly
in a thoughtless manner
Example: he stared thoughtlessly at the picture
