Source : Webster's Revised Unabridged Dictionary (1913)

Trilogy \Tril"o*gy\, n. [Gr. trilogi`a; pref. tri- (see {Tri-})
   + lo`gos speech, discourse: cf. F. trilogie.]
   A series of three dramas which, although each of them is in
   one sense complete, have a close mutual relation, and form
   one historical and poetical picture. Shakespeare's `` Henry
   VI.'' is an example.

         On the Greek stage, a drama, or acted story, consisted
         in reality of three dramas, called together a trilogy,
         and performed consecutively in the course of one day.
                                                  --Coleridge.

Source : WordNet®

trilogy
     n : a set of three literary or dramatic works related in subject
         or theme

Source : Free On-Line Dictionary of Computing

Trilogy
     
         A {strongly typed} {logic programming} language
        with numerical {constraint}-solving over the {natural
        numbers}, developed by Paul Voda 
        at {UBC} in 1988.  Trilogy is syntactically a blend of
        {Prolog}, {Lisp}, and {Pascal}.  It contains three types of
        {clauses}: {predicates} ({backtracking} but no assignable
        variables), procedures (if-then-else but no backtracking;
        assignable variables), and {subroutines} (like procedures, but
        with input and {system calls}; callable only from top level or
        from other subroutines).
     
        Development of Trilogy I stopped in 1991.  Trilogy II,
        developed by Paul Voda 1988-92, was a {declarative} general
        purpose programming language, used for teaching and to write
        {CL}.
     
        {(http://www.fmph.uniba.sk/~voda)}.
     
        ["The Constraint Language Trilogy: Semantics and
        Computations", P. Voda, Complete Logic Systems, 741 Blueridge
        Ave, North Vancouver BC, V7R 2J5].
     
        (2000-04-08)