A term used to describe a guy who is engaged in conversation and flirtacious behaviour with a girl he fancies.
Mike: "Hey Bob, did you see Jay and Nicola at lunch?
Bob: "No, why?
Mike: "Ohhh, lad, Jay was blaggin for sure"
someone who's making up a lie (in this case a blag) to hide something from someone, get something they want or even just to make conversation!!
sean: i blagged up gary yesterday to lend me his FIFA PS2 game
sandra (to linda): are you comin to my house tonight then?
linda: sorry i cant. i got work
bex: wat a blag!!