When someone acts like they are morally better than other people, especially when they are not really better.
Sanctimoniousness is usually seen as a bad thing because it can make people feel annoyed or angry.
Examples:
Her sanctimoniousness makes me feel bad about myself.
I don't like his sanctimoniousness.
The man's sanctimoniousness annoys everyone.
The sanctimoniousness of the politician is really funny.
The teacher's sanctimoniousness is so big, it fills the whole room.
The dog's sanctimoniousness is so big, it fills the whole house.