The Collaborative International Dictionary of English v.0.48:

Apparatus \Ap"pa*ratus\, n.; pl. Apparatus, also rarely
   Apparatuses. [L., from apparare, apparatum, to prepare; ad
   + prepare to make ready.]
   1. Things provided as means to some end.
      [1913 Webster]

   2. Hence: A full collection or set of implements, or
      utensils, for a given duty, experimental or operative; any
      complex instrument or appliance, mechanical or chemical,
      for a specific action or operation; machinery; mechanism.
      [1913 Webster]

   3. (Physiol.) A collection of organs all of which unite in a
      common function; as, the respiratory apparatus.
      [1913 Webster]

WordNet (r) 3.0 (2006):

apparatus
    n 1: equipment designed to serve a specific function [syn:
         apparatus, setup]
    2: (anatomy) a group of body parts that work together to perform
       a given function; "the breathing apparatus"

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "apparatus":
   Bunsen burner, Erlenmeyer flask, Kipp generator, accouterments,
   alembic, appliance, appliances, appointments, appurtenances,
   armament, aspirator, bag and baggage, baggage, beaker, blowpipe,
   burette, capillary tube, condenser, contraption, contrivance,
   conveniences, crucible, deflagrating spoon, desiccator, device,
   distiller, duffel, dunnage, equipage, equipment, etna, facilities,
   facility, fittings, fixtures, furnishings, furniture, gadget, gear,
   gimcrack, gimmick, gizmo, habiliments, hand tool, impedimenta,
   implement, installations, instrument, kit, luggage, machine,
   machinery, materiel, matrass, means, mechanical device, munition,
   munitions, outfit, paraphernalia, pestle and mortar, pipette,
   plant, plumbing, power tool, precision balance, precision tool,
   provisions, reagent bottle, receiver, retort, rig, rigging,
   speed tool, still, stock-in-trade, supplies, tackle, tackling,
   test tube, things, tool, traps, utensil, utensils