As in so much else, “dirty” has a lot to do with one’s personal comfort level, bodily acceptance, and the marital relationship. Mutual communication during intimacy is clearly appropriate and moral, as the needs of both partners need to be addressed. If, during intimacy, one of the spouses says something along the lines of “Please __________ my ____________,” I don’t think it’s necessary to use clinical / medical terms in making that request. I’m thinking that a loving couple has a “language of intimacy” they develop just as their physical relationship develops, and such expressions are mutually acceptable, confortable, and non-demeaning in and for that relationship.