The Collaborative International Dictionary of English v.0.48:

neonate \ne"o*nate\ (n[=e]"[-o]*n[=a]t), n.
   A newborn child, especially one less than one month old.

   Syn: baby, babe, infant.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

neonate
    n 1: a baby from birth to four weeks [syn: neonate, newborn,
         newborn infant, newborn baby]