A person, usually from the United Kingdom (see also: Gammon), who has their country's flag in their profile name or profile photo. Likely to be a paedophile (synonym - nonce).
Usually claim to be 'not a racist' but is that person who at any dinner party when the subject of racism becomes discussion will say "I'm not being racist, but".
The black flag nation or bfn is a group of faggoty teenagers in Murfreesboro, Tennessee, who think they are all cool and edgy because they are anarchists. They don't have members across the U.S. or Europe or Asia. No one from any government agency has ever investigated members of their group, because they don't do shit. Any crimes on their records probably aren't any worse than jaywalking.
P.S. their grammar is terrible.