I think you just said it: "Sex with a woman's breasts" is pretty good. It's perfectly appropriate when testifying before Congress and can even be added to your résumé if you have no other skills.

The clinical term, if you're interested, is "intermammary intercourse." "Intermammary," says Susan Quilliam, relationship psychologist and author of The New Joy of Sex, "as the act is performed between the breasts, not into them." (That would beintramammary, which is rarely practiced outside of killers' basements and some disreputable cosmetic-surgery centers.)

Of course, there are other ways in which people refer to the act, but I don't recommend them. Jesse Sheidlower, president of the American Dialect Society and author of The F-Word, speaks of a "Hawaiian muscle fuck," which seems a bit ambiguous, since I'm sure Dog and Beth Chapman aren't the only ones who do it. Additionally, James Joyce said something about "rosy-tipped bubbies" in a letter to his wife once, but I don't think he'd want the whole quote repeated here, since it's hardly his best effort. It's no "heaventree of stars hung with humid nightblue fruit" or anything.

All things considered, you might just say "titty fucking," like all well-adjusted people do, particularly if you're engaged in it and most definitely if you paid for them.