The Collaborative International Dictionary of English v.0.48:

Side \Side\, v. i. [imp. & p. p. Sided; p. pr. & vb. n.
   Siding.]
   1. To lean on one side. [Obs.] --Bacon.
      [1913 Webster]

   2. To embrace the opinions of one party, or engage in its
      interest, in opposition to another party; to take sides;
      as, to side with the ministerial party.
      [1913 Webster]

            All side in parties, and begin the attack. --Pope.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sided \Sid"ed\, a.
   Having (such or so many) sides; -- used in composition; as,
   one-sided; many-sided.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "sided":
   bifacial, bilateral, dihedral, flanked, handed, lateral,
   many-sided, multilateral, one-sided, polyhedral, quadrilateral,
   tetrahedral, three-sided, trihedral, trilateral, triquetrous,
   two-sided, unilateral