The Collaborative International Dictionary of English v.0.48:

Inborn \In"born`\, a.
   Born in or with; implanted by nature; innate; congenital; as,
   inborn passions. --Cowper.

   Syn: Innate; inherent; congenital; natural.

WordNet (r) 3.0 (2006):

inborn
    adj 1: present at birth but not necessarily hereditary; acquired
           during fetal development [syn: congenital, inborn,
           innate]
    2: normally existing at birth; "mankind's connatural sense of
       the good" [syn: connatural, inborn, inbred]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "inborn":
   atavistic, bodily, born, coeval, congenital, connatal, connate,
   connatural, constitutional, deep-rooted, deep-seated, genetic,
   hereditary, in the blood, inbred, incarnate, indigenous, ingrained,
   inherent, inherited, innate, instinctive, instinctual, native,
   native to, natural, natural to, organic, physical, primal,
   temperamental, tersely