What is No Da~!?
1.
-An expression said aloud to someone to let them know you know already.
-Used in a sarcastic tone of voice, often rolling your eyes upward gets the point across better. It can be a bit insulting too.
-Its like saying "why did you waste your time telling me that" gesture.
Easy example:
person1: "Red and Blue make Purple"
person2: "No Da! I know that!"
See