The Collaborative International Dictionary of English v.0.48:

cross-link \cross-link\ v. t. [imp. & p. p. cross-linked, p.
   pr. & vb. n. cross-linking.] (Chem., Biochem.)
   to create cross links in; -- of polymeric molecules.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

cross-link \cross-link\ n. (Chem., Biochem.)
   a covalent bond that links two chains of atoms, or two
   sections of one chain, in a polymeric molecule; the
   cross-link is created by a third bond in a monomer unit in
   addition to the two bonds forming the polymeric chain; -- a
   cross-link may be internal to a single chain, rather than
   between two otherwise unlinked chains; as, ultraviolet
   irradiation creates cross-links between the two chains of a
   DNA double helix; many enzymes have cross-links formed by
   disulfide bonds; polystyrene resins have their porosity
   controlled by the proportion of cross-links. Called also
   cross-linkage.

   Syn: cross-linkage.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

cross-link
    n 1: a side bond that links two adjacent chains of atoms in a
         complex molecule [syn: cross-link, cross-linkage]
    v 1: join by creating covalent bonds (of adjacent chains of a
         polymer or protein)