Source : Webster's Revised Unabridged Dictionary (1913)

      Looking round on every side beheld A pathless desert.
                                                  --Milton.

   4.
      (a) One of the halves of the body, of an animals or man,
          on either side of the mesial plane; or that which
          pertains to such a half; as, a side of beef; a side of
          sole leather.
      (b) The right or left part of the wall or trunk of the
          body; as, a pain in the side.

                One of the soldiers with a spear pierced his
                side.                             --John xix.
                                                  34.

   5. A slope or declivity, as of a hill, considered as opposed
      to another slope over the ridge.

            Along the side of yon small hill.     --Milton.

   6. The position of a person or party regarded as opposed to
      another person or party, whether as a rival or a foe; a
      body of advocates or partisans; a party; hence, the
      interest or cause which one maintains against another; a
      doctrine or view opposed to another.

            God on our side, doubt not of victory. --Shak.

            We have not always been of the . . . same side in
            politics.                             --Landor.

            Sets the passions on the side of truth. --Pope.

   7. A line of descent traced through one parent as
      distinguished from that traced through another.

            To sit upon thy father David's throne, By mother's
            side thy father.                      --Milton.

   8. Fig.: Aspect or part regarded as contrasted with some
      other; as, the bright side of poverty.

   {By the side of}, close at hand; near to.

   {Exterior side}. (Fort.) See {Exterior}, and Illust. of
      {Ravelin}.

   {Interior side} (Fort.), the line drawn from the center of
      one bastion to that of the next, or the line curtain
      produced to the two oblique radii in front. --H. L. Scott.

   {Side by side}, close together and abreast; in company or
      along with.

   {To choose sides}, to select those who shall compete, as in a
      game, on either side.

   {To take sides}, to attach one's self to, or give assistance
      to, one of two opposing sides or parties.

Source : WordNet®

side by side
     adj 1: nearest in space or position; immediately adjoining without
            intervening space; "had adjacent rooms"; "in the next
            room"; "the person sitting next to me"; "our rooms
            were side by side" [syn: {adjacent}, {next}, {side by
            side(p)}]
     2: closely related or associated; "a city in which communism
        and democracy had to live side by side"