When somebody is being both Snooty and Annoying at the exact same time..
Tends to be when somebody is full of themselves and being annoying about it.
Person 1: - What are you doing?
Person 2: - The Task.
Person 1: - Ohh right well I've already done that.
Person 2: - Shut up! I'm doing my work!
Person 1: - No you're not.
Person 2: - That's because you're snootying.