• Webster's Revised Unabridged Dictionary
    • Mammillary (Min) Composed of convex convex concretions, somewhat resembling the breasts in form; studded with small mammiform protuberances.
    • Mammillary Of or pertaining to the mammilla, or nipple, or to the breast; resembling a mammilla; mammilloid.
    • ***
Century Dictionary and Cyclopedia
    • mammillary Pertaining to a mamma, pap, dug, or teat.
    • mammillary Resembling a nipple.
    • mammillary Studded with mammiform protuberances; having rounded projections, as a mineral composed of convex concretions in form somewhat resembling breasts.
    • ***
Chambers's Twentieth Century Dictionary
    • adjs Mammillary pertaining to, or resembling, the breasts: studded with rounded projections
    • ***


Webster's Revised Unabridged Dictionary
Cf. F. mammilaire,. See Mammilla
Chambers's Twentieth Century Dictionary


In literature:

In various shapes, from sharp-edged crystals to mammillary-shaped nuggets of wood-tin; from masses of 30 lbs.
"Getting Gold" by J. C. F. Johnson
It occurs in mammillary rounded masses, with a fibrous structure, and a dull metallic lustre.
"Geology" by James Geikie
Much haematite occurs in a compact or massive form, often mammillary, and presenting on fracture a fibrous structure.
"Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7" by Various
Mammillary tuberosities not very prominent.
"Trees. A Woodland Notebook" by Herbert Maxwell
Mammillary tuberosities not very prominent.
"Extinct Birds" by Walter Rothschild

In news:

I'd never seen mammillary clouds before.
Mammillary clouds @ sunset.