The Collaborative International Dictionary of English v.0.48:

Pyx \Pyx\, n. [L. pyxis a box, Gr. pyxi`s a box, especially of
   boxwood, fr. py`xos the box tree or boxwood. See Box a
   receptacle.] [Written also pix.]
   1. (R. C. Ch.) The box, case, vase, or tabernacle, in which
      the host is reserved.
      [1913 Webster]

   2. A box used in the British mint as a place of deposit for
      certain sample coins taken for a trial of the weight and
      fineness of metal before it is sent from the mint.
      --Mushet.
      [1913 Webster]

   3. (Naut.) The box in which the compass is suspended; the
      binnacle. --Weale.
      [1913 Webster]

   4. (Anat.) Same as Pyxis.
      [1913 Webster]

   Pyx cloth (R. C. Ch.), a veil of silk or lace covering the
      pyx.

   Trial of the pyx, the annual testing, in the English mint,
      of the standard of gold and silver coins. --Encyc. Brit.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pyx \Pyx\, v. t.
   To test as to weight and fineness, as the coins deposited in
   the pyx. [Eng.] --Mushet.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pyx
    n 1: a chest in which coins from the mint are held to await
         assay [syn: pyx, pix, pyx chest, pix chest]
    2: any receptacle in which wafers for the Eucharist are kept
       [syn: pyx, pix]