Dun simply means "son". Originally started from a handicaped kid in Queens, NY. He couldn't pronounce son, so everytime he said son, it sounded more like dun. Mobb Deep coined the word and still use it today!

group of people, group of friends, posse that you chill with.

It is a slang word started out in Queens, NY

particularly the Queens bridge housing projects

It is a distortion of the word "Son" and is used to reference a friend or someone whose name you do not know

Short for "don't."

Originally used in greeting those who names are unknown to you or have been forgotten, dun has been revolutionized to act as a comma or pause in a sentence, indicating also that the following part is of significance and those around should stop what they are doing if possible and pay close attention. However "DUN" is also used when speaking with close friends and can take on several positions of a sentence.

It means Done

Also known as "Dave Dunning" is a sexual act in which one performs oral sex on a female's anus.