Green’s Dictionary of Slang

mosh v.²

to hit, to fight; to mess up, to destroy.

1953		W. Brown Run, Chico, Run (1959) 33: Every time Loco gets hung up he starts moshing me around.
1983		T. White Catch a Fire 139: Rude boys intent on ‘moshing up’ the [DJ] equipment.
2001		(con. 1981) A. Wheatle East of Acre Lane 158: De police dem moshing up people dem yard.

In phrases

mosh about (v.)

to mess about.

2000

F. Mac Anna Cartoon City 176: I’m concentrating on what I’m doing instead of moshing about. That’s why I’m minting it.