1. something you are aware of but not actively thinking about
what happened is still in the back of my mind
If something is 'in or at the back of your mind,' then it is constantly bothering or influencing you, even if you may not be fully conscious of it, like a nagging irritation. It can also be something that you know but just cannot recall, like the name of an acquaintance. If you put something 'to the back of your mind,' you try to stop it from affecting you by trying not to think about it. This expression is common in both a social and professional setting.