The Collaborative International Dictionary of English v.0.48:

Bivalent \Biv"a*lent\, a. [L. bis twice + valens, p. pr. See
   Valence.] (Chem.)
   Equivalent in combining or displacing power to two atoms of
   hydrogen; dyad.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bivalent
    adj 1: having a valence of two or having two valences [syn:
           bivalent, divalent]
    2: used of homologous chromosomes associated in pairs in
       synapsis [syn: bivalent, double] [ant: multivalent,
       univalent]