A culturally-intolerant person who complains when someone speaks a language other than the language of the referred-to person.
An English-speaking American who wants his cable TV company to remove Univision is a language nazi.
1. Someone who is generally intolerant of other languages/cultures.
2. Someone who insists that all people speak the language Nazi's preferred language.
1. "Billy Bob is such a language Nazi, because he punched those two Mexican guys for speaking Spanish. Either that or he's in the Tea Party."
2. Language Nazis are quite common in the Republic of Ireland, where some people want to force students to learn the moribund language that is Irish.