This is a Text message accranym that is sent from Paedophile to Paedophile. It means, Dusty Blonde Lulu, and thats a male paedophile disguised as a lion.
DBL is an abbreviation for double. This shortcut is usually used on forums when you are posting on a thread and think you didn't really click the post button but its just because of your crappy internet and you try to send the post again but the forums registers it as double posting.