wallbanging, n. — Green’s Dictionary of Slang

wallbanging n.

[SE bang, i.e. one ‘hits’ a wall]

(US gang) painting graffiti, esp. gang slogans or gang nicknames on walls.

1993		K. Scott Monster (1994) 52: Wallbangin’ (writing your name on a wall, advertising).
1999		S.A. Phillips Wallbangin’: Graffiti and Gangs in L.A.