grammar Nazi

Someone who insists on correcting or criticizing others for errors in spelling, grammar, and syntax, especially to a pedantic or self-righteous degree. Potentially offensive due to its reference to the fascist National Socialist German Workers' Party, which was brought to power in 1933 under Adolf Hitler. It irritates me to no end when people use "good" as an adverb, but I try not to be a grammar Nazi about it. A: "What are you, a grammar Nazi?" B: "Hardly. Everyone knows you shouldn't use 'ain't' in a formal paper."