polymastia; pleomastia; hypermastia
Medical term for the congenital condition of having more than two breasts or nipples. Used in clinical contexts.
Polymastia is a congenital condition in which more breast tissue than usual is present.
Refers specifically to supernumerary nipples, whereas 多乳房症 involves extra breast tissue or full breasts.
Compound of 多 (た, 'many'), 乳房 (にゅうぼう, 'breast'), and 症 (しょう, 'condition' or 'disease'). A straightforward medical coinage.