The Collaborative International Dictionary of English v.0.48:

Symmetrize \Sym"me*trize\, v. t. [imp. & p. p. Symmetrized; p.
   pr. & vb. n. Symmetrizing.] [Cf. F. sym['e]triser.]
   To make proportional in its parts; to reduce to symmetry.
   --Burke.
   [1913 Webster]