The act of perfroming oral or mutual masterbation of the digits to a female whilst she is operating a motor vehicle.
"Dude we took a road trip last weekend and I went muff-driving in 14 different states! Buiiiiiii."
"Susan, Im super worried my parents will find out Jake was muff-driving me when I hit that tree on 7th Ave last week..."
"We just met, and this is crazy, but I'm gonna muff-drive the shit out of you."