inconsideration
Not caring how your actions affect other people.
Inconsideration means acting without thinking about how your choices affect other people. When you show inconsideration, you're being thoughtless or careless about others' feelings, needs, or situations.
If you slam your locker door while someone's reaching into the one next to yours, that's inconsideration. You weren't trying to be mean, but you didn't think about the person beside you. When someone talks loudly during a movie, plays music without headphones on the bus, or cuts in line, they're showing inconsideration. They're so focused on what they want that they forget other people are around.
Inconsideration is different from deliberate cruelty. A person being inconsiderate usually isn't trying to hurt anyone. They're just not paying attention or thinking ahead. Even so, if your friend always shows up late when you've made plans, their inconsideration still wastes your time and suggests they don't value it.
The opposite is consideration, which means thinking about how your actions affect others. When you hold a door for someone carrying packages or keep your voice down in the library, you're showing consideration. Most people display inconsideration occasionally, but when it becomes a pattern, it damages friendships and makes others not want to be around you.