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]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "infancy":
   babyhood, beginnings, birth, callowness, childhood, commencement,
   cradle, dawn, dewiness, disability, disablement, disqualification,
   early, emergence, freshman year, freshness, genesis, greenness,
   imbecility, immaturity, inability, inadequacy, incapability,
   incapacitation, incapacity, inception, inchoation, incipience,
   incipiency, incompetence, incompetency, incunabula, inefficiency,
   ineptitude, inexperience, inferiority, initial, insufficiency,
   juiciness, juniority, juvenility, legal incapacity, minority,
   my Angel-infancy, nascence, nascency, nativity, nonage, origin,
   origination, parturition, pregnancy, rawness, rise, sappiness,
   stages, start, the nursery, undevelopment, unfitness, unripeness,
   wardship, youth



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.