Combination of two things, the Hersey Highway and the Tittie Fuck. Since doing someone up the ass is called doing the hersey highway, and doing someone's tits is called a tittie fuck, by combining them you get the Frontage Road. What you do is fuck their ass cheeks, but don't actually enter the asshole. For those that don't know a frontage road is the road that runs along a highway, and sometimes is what's used to get on the highway. It's your choice if shit is involved, cause it's not necessary, but sure is fun!
Girl: God my ass hurts!
Guy: Why, mexican food?
Girl: No, Todd gave me a Frontage Road last night, and we didn't have lube.