Secular, uncensored Urban Dictionary has a line or two I love on this wonderful relationship:
ANR/ABF stands for: A Nursing Relationship/Adult Breast Feeding. ANR/ABF refers to a relationship involving sucking milk from the female breast as an expression of close intimacy. Adult Nursing Relationships depend on a stable and long term relationship of the couple, otherwise it is nearly impossible to maintain a steady milk flow. On the other hand it is frequently reported that breastfeeding has a strong stabilizing effect on the partnership [emphases mine]. The breastfeeding woman may experience orgasms or a pleasurable let-down reflex.
Examples of usage of the term ANR/ABF:
I could totally go ANR on that [large-breasted woman!] (you’re free to indulge if she’s your wife)
alt: I could totally go ABF on that [large-breasted woman!] (you too, go ahead if you’re married)