To press your mouth and cheeks tightly into your partner's dirty ass crack and go "phhhbbbsssffft" so hard that you get an arc of poo on your face, hence, the "chocolate frown".
"Damn, that bitch got all up in my grill, so I told her to get down there and get her bitch-ass face a chocolate frown."
by ubiquitron May 4, 2006