The Collaborative International Dictionary of English v.0.48:

Mamma \Mam*ma"\, n. [Reduplicated from the infantine word ma,
   influenced in spelling by L. mamma.]
   Mother; -- word of tenderness and familiarity. [Written also
   mama.]
   [1913 Webster]

         Tell tales papa and mamma.               --Swift.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mamma \Mam"ma\, n.; pl. Mammae. [L. mamma breast.] (Anat.)
   A glandular organ for secreting milk, characteristic of all
   mammals, but usually rudimentary in the male; a mammary
   gland; a breast; udder; bag.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mamma
    n 1: informal terms for a mother [syn: ma, mama, mamma,
         mom, momma, mommy, mammy, mum, mummy]
    2: milk-secreting organ of female mammals [syn: mammary gland,
       mamma]