DA means district attorney. The relevance of this and urban terminology is it's connection with punishment for crimes. If you get caught by the 'Po (
police for yall) selling drugs or whatnot, you will probably have to deal with a District Attorney. District Attorneys only practice
law in district courts (imagine that). If you murder someone or get caught with enough
coke to make a state, or even worse, a federal
case, you won't be dealing with a DA, you'll be fucking with a whole new ballpark of lawyers and attorneys.