The Collaborative International Dictionary of English v.0.48:

Chassis \Chas"sis\, n. [F. ch[^a]ssis.] (Mil.)
   1. A traversing base frame, or movable railway, along which
      the carriage of a barbette or casemate gun moves backward
      and forward. [See Gun carriage.]
      [1913 Webster]

   2. The under part of an automobile or other motor vehicle,
      consisting of the frame (on which the body is mounted)
      with the wheels and machinery.
      [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

chassis
    n 1: alternative names for the body of a human being; "Leonardo
         studied the human body"; "he has a strong physique"; "the
         spirit is willing but the flesh is weak" [syn: human
         body, physical body, material body, soma, build,
         figure, physique, anatomy, shape, bod, chassis,
         frame, form, flesh]
    2: a metal mounting for the circuit components of an electronic
       device
    3: the skeleton of a motor vehicle consisting of a steel frame
       supported on springs that holds the body and motor

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "chassis":
   backing, base, baseboard, basement, bearing, bushing, cabinet,
   cadre, case, casement, casing, console, dado, doorframe, fabric,
   foot, footing, foundation, frame, framework, framing, housing,
   infrastructure, keel, lattice, latticework, mopboard, mount,
   mounting, nadir, picture frame, radio, radio receiver, radio set,
   radio telescope, receiver, receiving set, sash, set, setting,
   shell, shoemold, skeleton, sole, toe, underframe, wainscot,
   window case, window frame, wireless, wireless set