To engage in the act of coitus with an overweight girl, but with extreme physical force and a great passion.
Drunken sex can often be classified as a "Moby Dicking", due to the lack of judgement, but the intact passion of lovemaking.
"Can you believe Hank beats his girlfriend?"
"Yeah, I heard about that. I bet when they're alone she gets a solid Moby Dicking."
“To the ass, I grapple with thee; From Hell's heart, I hump at thee; For hate's sake, I shoot my last load at thee!"