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."
Offender: My family are all idiots. I mean, I'm never stop having to suffer their genocide.
You: Suffering? you don't know the meaning of the word.
by Tevel February 19, 2014