A man who rapes or beats his nephews and nieces or other children, or treats children like dirt. Originally a character from the book Once Were Warriors by Alan Duff, which was also made into a movie.
A man who asked 5 boys in his care to call him "Uncle Bully" was recently arrested for assault.
You're no better than Uncle Bully, I should cut your dick off!
A term for a rapist or someone whose just a dirty c*nt, can also be shouted at your local if you want someone to buy you a round STAT!!!
"Guy walks into a bar and yells UNCLE F*CKEN BUUUULLLLYYYYYY!!!!"
"locals buy the guy beers so he doesnt beat the sh*t outta them"
Man rapes a woman, his friends go "yuck what an uncle bully".