The Collaborative International Dictionary of English v.0.48:

Infancy \In"fan*cy\, n. [L. infantia: cf. F. enfance. See
   Infant.]
   [1913 Webster]
   1. The state or period of being an infant; the first part of
      life; early childhood.
      [1913 Webster]

            The babe yet lies in smiling infancy. --Milton.
      [1913 Webster]

            Their love in early infancy began.    --Dryden.
      [1913 Webster]

   2. The first age of anything; the beginning or early period
      of existence; as, the infancy of an art.
      [1913 Webster]

            The infancy and the grandeur of Rome. --Arbuthnot.
      [1913 Webster]

   3. (Law) The state or condition of one under age, or under
      the age of twenty-one years; nonage; minority.
      [1913 Webster]

WordNet (r) 3.0 (2006):

infancy
    n 1: the early stage of growth or development [syn: infancy,
         babyhood, early childhood]
    2: the earliest state of immaturity [syn: infancy, babyhood]

The Devil's Dictionary (1881-1906):

INFANCY, n.  The period of our lives when, according to Wordsworth,
"Heaven lies about us."  The world begins lying about us pretty soon
afterward.