'Grunja' is a term now used by ignorant Chavs who are still taught that they should spell how they would say a word, and with their Janner accent it's no surprise that they could come up with a new word such as 'Grunja', 'Grunja' is actually just their dumb little way of stereotyping a Greebo (arch enemy of the Chav) as a Grunger.

No Bull Shit, and old hacker acronym which is usually used to signify that the talk will be serious.