Source : Webster's Revised Unabridged Dictionary (1913)

Lactation \Lac*ta"tion\, n.
   A giving suck; the secretion and yielding of milk by the
   mammary gland.

Source : WordNet®

lactation
     n 1: the period following birth during which milk is secreted;
          "lactation normally continues until weaning"
     2: the production and secretion of milk by the mammary glands
     3: feeding an infant by giving suck at the breast [syn: {suckling}]