NOT!

NOT! Is a grammatical construction used in the English language as a slang term that became a popular sarcastic catch phrase in the 1990s in North America. During its most popular time in the 1990s, mostly teenagers and young adults used this phrase. It is not commonly used today, but its meaning refers to someone not agreeing with what has been said to them, as a way to deny what is being said in a sarcastic way.