Green’s Dictionary of Slang

(US campus) to offend by making sexual remarks or using offensive language.

1974		Eble Campus Sl. Mar. 5: raunch someone out [...] Bob was trying to raunch out the priest at confession.
1996		Eble Sl. and Sociability 30: In college slang out is the most productive particle: [...] raunch out ‘offend by making sexual remarks or using offensive language’.