To obtain (something) for free, particularly by guile or persuasion.
Can I blag a fag?
(specifically) To obtain confidential information by impersonation or other deception.
The newspaper is accused of blagging details of Gordon Brown's flat purchase from his solicitors.
To pick up someone.
(1960s) To inveigle by persuasion.
He's blagged his way into many a party.
(1940s) To deceive; to perpetrate a hoax on.
A robbery.