Source : Webster's Revised Unabridged Dictionary (1913)

Closure \Clo"sure\ (?, 135), n. [Of. closure, L. clausura, fr.
   clauedere to shut. See {Close}, v. t.]
   1. The act of shutting; a closing; as, the closure of a
      chink.

   2. That which closes or shuts; that by which separate parts
      are fastened or closed.

            Without a seal, wafer, or any closure whatever.
                                                  --Pope.

   3. That which incloses or confines; an inclosure.

            O thou bloody prison . . . Within the guilty closure
            of thy walls Richard the Second here was hacked to
            death.                                --Shak.

   4. A conclusion; an end. [Obs.] --Shak.

   5. (Parliamentary Practice) A method of putting an end to
      debate and securing an immediate vote upon a measure
      before a legislative body. It is similar in effect to the
      previous question. It was first introduced into the
      British House of Commons in 1882. The French word
      {cl[^o]ture} was originally applied to this proceeding.

Source : WordNet®

closure
     n 1: approaching a particular destination; a coming closer; a
          narrowing of a gap; "the ship's rapid rate of closing
          gave them little time to avoid a collision" [syn: {closing}]
     2: a rule for limiting or ending debate in a deliberative body
        [syn: {cloture}, {gag rule}, {gag law}]
     3: a Gestalt principle of organization holding that there is an
        innate tendency to perceive incomplete objects as complete
        and to close or fill gaps and to perceive asymmetric
        stimuli as symmetric [syn: {law of closure}]
     4: something settled or resolved; the outcome of decision
        making; "the finally reached a settlement with the union";
        "they never did achieve a final resolution of their
        differences"; "he needed to grieve before he could achieve
        a sense of closure" [syn: {settlement}, {resolution}]
     5: an obstruction in a pipe or tube; "we had to call a plumber
        to clear out the blockage in the drainpipe" [syn: {blockage},
         {block}, {occlusion}, {stop}, {stoppage}]
     6: the act of blocking [syn: {blockage}, {occlusion}]
     7: termination of operations; "they regretted the closure of
        the day care center" [syn: {closedown}, {closing}, {shutdown}]
     v : terminate debate by calling for a vote; "debate was
         closured"; "cloture the discussion" [syn: {cloture}]

Source : Free On-Line Dictionary of Computing

closure
     
        1.  In a {reduction system}, a closure is a data
        structure that holds an expression and an environment of
        variable bindings in which that expression is to be evaluated.
        The variables may be local or global.  Closures are used to
        represent unevaluated expressions when implementing
        {functional programming languages} with {lazy evaluation}.  In
        a real implementation, both expression and environment are
        represented by pointers.
     
        A {suspension} is a closure which includes a flag to say
        whether or not it has been evaluated.  The term "{thunk}" has
        come to be synonymous with "closure" but originated outside
        {functional programming}.
     
        2.  In {domain theory}, given a {partially ordered
        set}, D and a subset, X of D, the upward closure of X in D is
        the union over all x in X of the sets of all d in D such that
        x <= d.  Thus the upward closure of X in D contains the
        elements of X and any greater element of D.  A set is "upward
        closed" if it is the same as its upward closure, i.e. any d
        greater than an element is also an element.  The downward
        closure (or "left closure") is similar but with d <= x.  A
        downward closed set is one for which any d less than an
        element is also an element.
     
        ("<=" is written in {LaTeX} as {\subseteq} and the upward
        closure of X in D is written \uparrow_\{D} X).
     
        (1994-12-16)