I don't even know what that means
This phrase is used when you're too scared to admit you're clueless and you're too lazy to look it up.
He said, 'I don't even know what that means,' after I told him the movie was about a robot.
She said, 'I don't even know what that means,' when I asked her what a sentence was.
He said, 'I don't even know what that means,' after I told him the president was in a fight.