The Collaborative International Dictionary of English v.0.48:

switchboard \switch"board`\ n.
   1. an elctrical apparatus consisting predominantly of a panel
      on which are switches or other means of completing
      electrical circuits; -- used especially for the devices
      used in telephone exchanges. See sense 2.
      [PJC]

   2. (Telephone) An apparatus containing switches by means of
      which a connection may be made from an incoming telephone
      line to any one of numerous outgoing lines. The switches
      may be either mechanical or electronic, and the switching
      action may be automatic, controlled by signals in the
      incoming call, or manual, controlled by a switchboard
      operator. In older style manual switchboards, the circuits
      were connected by the use of patchcords, inserted into
      plugs.

   Syn: patchboard, plugboard, telephone exchange.
        [PJC]

WordNet (r) 3.0 (2006):

switchboard
    n 1: telephone central where circuits are completed with
         patchcords [syn: switchboard, patchboard, plugboard]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "switchboard":
   A board, B board, L, PBX, R, acting area, apron, apron stage,
   backstage, band shell, bandstand, board, bridge, coulisse, dock,
   dressing room, flies, fly floor, fly gallery, forestage, greenroom,
   grid, gridiron, lightboard, orchestra, orchestra pit,
   performing area, pit, proscenium, proscenium stage, shell, stage,
   stage left, stage right, the boards, wings