Green’s Dictionary of Slang

1. to live extravagantly, in a showy manner.

1998		Guardian 23 Oct. 16: He’s out on River Street larging it.
2000		J.J. Connolly Layer Cake 161: He was largin it.
2008		J. Niven Kill Your Friends (2009) 32: We’re larging it, mate!

2. to show off, to act aggressively.

2003

N. Griffiths Stump 49: Tommy’s there, fuckin largin it, givin it all the Godfather shite, holds a blade to the mudderfucker’s nose.