The Collaborative International Dictionary of English v.0.48:

Z \Z\ (z[=e]; in England commonly, and in America sometimes,
   z[e^]d; formerly, also, [i^]z"z[e^]rd)
   Z, the twenty-sixth and last letter of the English alphabet,
   is a vocal consonant. It is taken from the Latin letter Z,
   which came from the Greek alphabet, this having it from a
   Semitic source. The ultimate origin is probably Egyptian.
   Etymologically, it is most closely related to s, y, and j; as
   in glass, glaze; E. yoke, Gr. ?, L. yugum; E. zealous,
   jealous. See Guide to Pronunciation, [sect][sect] 273, 274.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Z
    n 1: the ending of a series or sequence; "the Alpha and the
         Omega, the first and the last, the beginning and the end"--
         Revelation [syn: omega, Z]
    2: the 26th letter of the Roman alphabet; "the British call Z
       zed and the Scots call it ezed but Americans call it zee";
       "he doesn't know A from izzard" [syn: Z, z, zee, zed,
       ezed, izzard]

The Free On-line Dictionary of Computing (30 December 2018):

Z

   /zed/  1. (After Zermelo-Fränkel set
   theory) A specification language developed by the
   Programming Research Group at Oxford University around 1980.
   Z is used for describing and modelling computing systems.  It
   is based on axiomatic set theory and first order predicate
   logic.  Z is written using many non-ASCII symbols.  It was
   used in the IBM CICS project.

   See also Z++.

   ["Understanding Z", J.M. Spivey, Cambridge U Press 1988].

   2.  A stack-based, complex arithmetic
   simulation language from ZOLA Technologies.

   (1995-08-11)