Source : Webster's Revised Unabridged Dictionary (1913)

Symmetrical \Sym*met"ric*al\, a. [Cf. F. sym['e]trique. See
   {Symmetry}.]
   1. Involving or exhibiting symmetry; proportional in parts;
      having its parts in due proportion as to dimensions; as, a
      symmetrical body or building.

   2. (Biol.) Having the organs or parts of one side
      corresponding with those of the other; having the parts in
      two or more series of organs the same in number;
      exhibiting a symmetry. See {Symmetry}, 2.

   3. (Bot.)
      (a) Having an equal number of parts in the successive
          circles of floral organs; -- said of flowers.
      (b) Having a likeness in the form and size of floral
          organs of the same kind; regular.

   4. (Math.) Having a common measure; commensurable.
      (b) Having corresponding parts or relations.

   Note: A curve or a plane figure is symmetrical with respect
         to a given line, and a line, surface, or solid with
         respect to a plane, when for each point on one side of
         the line or plane there is a corresponding point on the
         other side, so situated that the line joining the two
         corresponding points is perpendicular to the line or
         plane and is bisected by it. Two solids are symmetrical
         when they are so situated with respect to an
         intervening plane that the several points of their
         surfaces thus correspond to each other in position and
         distance. In analysis, an expression is symmetrical
         with respect to several letters when any two of them
         may change places without affecting the expression; as,
         the expression a^{2}b + ab^{2} + a^{2}c + ac^{2} +
         b^{2}c + bc^{2}, is symmetrical with respect to the
         letters a, b, c. -- {Sym*met"ric*al*ly}, adv. --
         {Sym*met"ric*al*ness}, n.

Source : WordNet®

symmetrically
     adv : in a symmetrical manner; "they were symmetrically arranged"
           [ant: {asymmetrically}]