Source : Webster's Revised Unabridged Dictionary (1913)

Mammilla \Mam*mil"la\, n.; pl. {Mammil[ae]}. [L., dim. of mamma
   a breast.] (Anat.)
   The nipple.

Source : WordNet®

mammilla
     n : the small projection of a mammary gland [syn: {nipple}, {mamilla},
          {pap}, {teat}, {tit}]
     [also: {mammillae} (pl)]