A spelling Nazi is a member of a forum who constantly points out minor spelling errors, grammatical errors and typos in other members' posts. Usually the spelling Nazi makes one or several errors doing this in a twisted case of irony. Spelling Nazis are sometimes referred to as grammar fascists.
The appearance of a spelling Nazi is highly correlated with the propensity for being on the losing end of arguments.
Spelling Nazis are essential for the mental health of the membership of an internet forum.