The Collaborative International Dictionary of English v.0.48:

Trapezium \Tra*pe"zi*um\, n.; pl. E. Trapeziums, L.
   Trapezia. [NL., fr. Gr. ? a little table, an irregular
   four-sided figure, dim. of ? a table, for ?; ? (see Tetra-)
   + ? foot, akin to ? foot; hence, originally, a table with
   four feet. See Foot.]
   1. (Geom.) A plane figure bounded by four right lines, of
      which no two are parallel.
      [1913 Webster]

   2. (Anat.)
      (a) A bone of the carpus at the base of the first
          metacarpal, or thumb.
      (b) A region on the ventral side of the brain, either just
          back of the pons Varolii, or, as in man, covered by
          the posterior extension of its transverse fibers.
          [1913 Webster]

WordNet (r) 3.0 (2006):

trapezium
    n 1: a quadrilateral with no parallel sides [ant:
         parallelogram]
    2: a multiple star in the constellation of Orion
    3: the wrist bone on the thumb side of the hand that articulates
       with the 1st and 2nd metacarpals [syn: trapezium,
       trapezium bone, os trapezium]