Verb - to face dirty someone
1. To insult someone personally, Usually by disclosing information in public, which they do not wish to be known.
Adverb - to be face dirty
2. Calling someone "Face Dirty" mean's that they have dissed someone, and you generally disapprove.
1.
Guy: I heard she sucked 4 d**ks in ONE NIGHT.
Girl: WHAT!?!
Spectator: OOOHHHH face dirtyyyy.
2.
Girl: Hahaha he thinks he's so good, but he sucks at every sport! He's black, but can't even play basketball!
Spectator: Damn! She's a haterrr! You so face dirty!!
When a woman with copious amounts of pubic hair sits on a man's face and rubs her vagina over his mouth. The dirty part comes in when the woman defecates on the man's face and rubs it over him with her pubies.