Source : Webster's Revised Unabridged Dictionary (1913)

Opal \O"pal\, n. [L. opalus: cf. Gr. ?, Skr. upala a rock,
   stone, precious stone: cf. F. opale.] (Min.)
   A mineral consisting, like quartz, of silica, but inferior to
   quartz in hardness and specific gravity.

   Note: The precious opal presents a peculiar play of colors of
         delicate tints, and is highly esteemed as a gem. One
         kind, with a varied play of color in a reddish ground,
         is called the harlequin opal. The fire opal has colors
         like the red and yellow of flame. Common opal has a
         milky appearance. Menilite is a brown impure variety,
         occurring in concretions at Menilmontant, near Paris.
         Other varieties are cacholong, girasol, hyalite, and
         geyserite.

Source : WordNet®

opal
     n : a translucent mineral consisting of hydrated silica of
         variable color; some varieties are used as gemstones

Source : Free On-Line Dictionary of Computing

Opal
     
        1. A {DSP} language.
     
        ["OPAL: A High Level Language and Environment for DSP boards
        on PC", J.P. Schwartz et al, Proc ICASSP-89, 1989].
     
        2. The language of the {object-oriented database} {GemStone}.
     
        ["Making Smalltalk a Database System", G. Copeland et al, Proc
        SIGMOD'84, ACM 1984, pp.316- 325].
     
        3. A {simulation} language with provision for {stochastic
        variable}s.  An extension of {Autostat}.
     
        ["C-E-I-R OPAL", D. Pilling, Internal Report,
        C.E.I.R. Ltd. (1963)].
     
        4. A language for compiler testing said to be used internally
        by {DEC}.
     
        5. A {functional programming} language designed at the
        {Technische Universitaet Berlin} as a testbed for the
        development of {functional program}s.  OPAL integrates
        concepts from Algebraic Specification and Functional
        Programming, which favour the (formal) development of (large)
        production-quality software written in a {purely functional}
        style.
     
        The core of OPAL is a {strongly typed}, {higher-order},
        {strict} applicative language which belongs to the tradition
        of {Hope} and {ML}.  The algebraic flavour of OPAL is visible
        in the syntactical appearance and in the preference of
        {parameterisation} to {polymorphism}.
     
        OPAL supports: {information hiding} - each language unit is
        divided into an interface (signature) and an implementation
        part; selective import; {parameterised module}s; free
        constructor {views} on {sorts}, which allow pattern-based
        function definitions despite quite different implementations;
        full {overloading} of names; puristic scheme language with no
        {built-in} data types (except {Boolean}s and denotations).
     
        OPAL and its predecessor OPAL-0 have been used for some time
        at the Technische Universitaet Berlin in CS courses and for
        research into optimising compilers for applicative languages.
        The OPAL compiler itself is writte entirely in OPAL.
     
        An overview is given in "OPAL: Design And Implementation of an
        Algebraic Programming Language".
     
        {Home (http://www.cs.tu-berlin.de/~opal/)}.
     
       
     {(ftp://ftp.cs.tu-berlin.de/pub/local/uebb/papers/DesignImplOpal.ps.gz)}.
     
        (1995-02-16)