mam·mil·lary \ˈmaməˌlerē, -ri\adjective Etymology: Latin mammilla breast, nipple + English -ary — more at mammilla 1.: of or relatng to the breasts 2. a.: having the form of a rounded eminence b.: composed of concretions shaped somewhat like breasts : studded with mammiform protuberances < limonite frequently occurs in mammillary masses >