Green’s Dictionary of Slang

(US gang) the attacking of another gang.

1993		K. Scott Monster (1994) 207: The Crips [...] were then plagued – indeed, traumatized – by the internal strife of ‘set trippin’’.
2002		‘Touré’ Portable Promised Land (ms.) 158: We Words (My Favorite Things) [...] Never slippin. Set trippin. Steady mobbin. Keep steppin.