A person who spends a lot of time on Internet baby names discussion boards, making it her business to instruct others, in an authoritarian manner, as to what they should or should not name their babies.
The typical name nazi tends to be female and conservative, and will berate and ridicule anyone whose tastes deviate from those of the herd.
Her cautionary catchphrase consists of: "Other children will make fun of your child if you name her that!" Ironically, the brandished, name-teasing schoolyard bullies are most likely to be the offspring of the name nazis themselves, having learned their behavior from their mothers.
She posted that she was thinking of naming her baby "Indigo" and, omg, the board's name nazis all jumped on her.
A douche-bag who exploits the EULA of a MMO videogame by reporting "offensive" names of other players in order to exact revenge for losing.
OMG some name nazi reported my name as offensive, and this GM changed it from "Cawkrawker" to "Jibartl".