Green’s Dictionary of Slang

(US campus) to leave.

1992		Eble Campus Sl. Apr. 7: peace out – leave.
2005		A. Swartz ‘Sweet, Tight and Hella Stupid’ in S.F. University High School Update Mar.–Apr. 2: We’re gonna peace them – we’re leaving or ditching them.
2012		M. Lacher On the Bro’d 33: ‘How about you and me trawl for tang [...] before you peace out’.