DBL stands for the Dick Biting Look. It's the look a girl gives you were you just KNOW she wants to suck on your business all night long! Like you'll walk by and she breaks her neck to get a better look at you, THAT is the DBL. A beautiful thing really
"Hey man Sharon is giving you the DBL over there, you better go get her number!"
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.