To be a 'bronno' or more commonly 'a derty bronno'.. is to be a chatty bastard.
Behaviour that is likely to trigger this particular insult includes picking and eating one's bogeys/earwax etc, eating or drinking something you 'found' on an empty table in a pub, or any other foul activity that might be expected of a scally.
Can be used semi-affectionately amongst the sort of very close friends who greet each other with a friendly 'alright cunt, not seen you in fucking time'.
Used in parts of North Nottingham.
"yer derty bronno"
"Wot you anging around with that filthy bronno for?"