A term originating from London used to describe a gangster or a rebel who does not respect authority. Often associated with urban culture, UK rap etc..
One can also use the term as a sarcastic insult..i.e if a person thinks they are "bad" but is conceived to be a pussy by others
person A "yo bro im running tingz around dese endz" ...
Person B "your sick blad, your a badman"