You don't know the meaning of the word
The statement is said to express
ire and/or contempt. When someone says it, they are saying that the person who used the aforementioned adjective should not be using it, as they don't truly know what it means to feel it. I.E. you had your face melted off, and you broke
the arm of someone who pissed you off. You would say "Painful?
You don't know the meaning of the word."