polymastia

poly- +‎ -mastia (corresponding to Ancient Greek μαστός (mastós, “breast”)).

• IPA^(key): /pɒlɪˈmæstɪə/

polymastia (uncountable)

1. The fact or condition of having more than two mammae or nipples.
   • 1878 April 6, “Reviews and notices of books: On Numerical Anomalies of the Breast”, in The Lancet, volume 114, page 500:

     Viewed in the light of comparative anatomy, polymastia is interesting, as showing a tendency to re-establish the series of mammae seen in other mammalia; but Darwin has lately repudiated atavism as a cause of this malformation

   • 1976, Kyril Bonfiglioli, Something Nasty in the Woodshed, Penguin, published 2001, page 420:

     The warts on its skin, you see, remind one of the extra nipples which every she-witch was supposed to have and that goes back (am I boring you, dear boy? How is your glass?) that goes back to the polymastia or superfluity of breasts of the ancients.