Someone that points out the most slightest grammar or spelling mistake. The most innocent of people can briefly turn into something so low called a grammar nazi. They evolve when insecurity in heated arguments arise when a fault with one of the opponents spelling or grammar must be pointed out as an utter write-off excuse. A grammar comeback isn't a diss or even an ownage on any sort of level to begin with despite how well placed it could be. It's one of the worst cop out excuses of a finish/settlement driven by people that make it even more pathetic when "umadbro?'s" (angry people) use it over "the internetz" (the internet). Just from the fact that society accepts improper grammar this day and age for example a movie that might be called "I spie with my little i" makes grammar comebacks an automatic backfire period.

a person who does not like incorrect grammar

A person who finds it fun to correct the incorrect spelling and grammar of noobs and idiots.

A persobn who surfs the internet correct people's mis-spellings, and grammatical errors.

In internet forums, they are the homos who thwart arguments not with logic or intelligence but by pointing out mistakes in spelling or syntax. When this happens, the original post preceding the edited quote, no matter the quality of the conceptual content, or how good of an argument is made, is apparently rendered useless and pointless, for having a simple grammatical error. What the grammar nazis (who should more correctly be termed grammar fags) don't realize, is that it is their role as an editor in a conversation in an informal writing environment that is useless. Even the greatest writers make mistakes now and then--stay off the internet.

They are very similar to the internet troll.

An idiot.
1) Someone who is too stupid to think of a reasoned response to any argument so resorts to attacking someone's grammar and spelling instead.

2) Someone who has failed to grasp that forums are not in fact English essays. Language has always varied according to context, just as we use different types of words in a job interview compared to with our mates.

3) Usually in English forums monolingual native English speakers who utterly FAIL do to the fact that 60% of times they are criticizing someone who is using English as a second language at a far higher standard than the grammar nazi would ever be able to use a second language themselves. 30% of remaining cases the person they are talking to is native English but is dyslexic or 10 years younger. And all 100% of times the person being criticized has much better things to do with their time than correct their every spelling mistake. In either case the grammar nazi fails!

4) Someone unable to figure out the difference between intelligence and correct grammar and spelling.

A Grammar Nazi is often either
1. A teacher, most commonly an English teacher, who will give a student an F on his/her paper because they used "they're" instead of "their" or "to" instead of "too".
2. A blogger who feels the need to go to as many sites as possible to correct their grammar or spelling.

Despite popular belief, the world does need a few grammar nazis, if you would beleive that.