Source : Webster's Revised Unabridged Dictionary (1913)

Portal \Por"tal\, n. [OF. portal, F. portail, LL. portale, fr.
   L. porta a gate. See {Port} a gate.]
   1. A door or gate; hence, a way of entrance or exit,
      especially one that is grand and imposing.

            Thick with sparkling orient gems The portal shone.
                                                  --Milton.

            From out the fiery portal of the east. --Shak.

   2. (Arch.)
      (a) The lesser gate, where there are two of different
          dimensions.
      (b) Formerly, a small square corner in a room separated
          from the rest of the apartment by wainscoting, forming
          a short passage to another apartment.
      (c) By analogy with the French portail, used by recent
          writers for the whole architectural composition which
          surrounds and includes the doorways and porches of a
          church.

   3. (Bridge Building) The space, at one end, between opposite
      trusses when these are terminated by inclined braces.

   4. A prayer book or breviary; a portass. [Obs.]

   {Portal bracing} (Bridge Building), a combination of struts
      and ties which lie in the plane of the inclined braces at
      a portal, serving to transfer wind pressure from the upper
      parts of the trusses to an abutment or pier of the bridge.

Portal \Por"tal\, a. (Anat.)
   Of or pertaining to a porta, especially the porta of the
   liver; as, the portal vein, which enters the liver at the
   porta, and divides into capillaries after the manner of an
   artery.

   Note: Portal is applied to other veins which break up into
         capillaries; as, the renal portal veins in the frog.

Source : WordNet®

portal
     n 1: a grand and imposing entrance (often extended
          metaphorically); "the portals of the cathedral"; "the
          portals of heaven"; "the portals of success"
     2: a site that the owner positions as an entrance to other
        sites on the internet; "a portal typically has search
        engines and free email and chat rooms etc." [syn: {portal
        site}]
     3: a short vein that carries blood into the liver [syn: {portal
        vein}, {hepatic portal vein}, {vena portae}]

Source : Free On-Line Dictionary of Computing

PORTAL
     
        Process-Oriented Real-Time Algorithmic Language.
     
        ["PORTAL - A Pascal-based Real-Time Programming Language",
        R. Schild in Algorithmic Languages, J.W. deBakker et al eds,
        N-H 1981].

portal
     
         A {web site} that aims to be an entry point
        to the {World-Wide Web}, typically offering a {search engine}
        and/or links to useful pages, and possibly news or other
        services.  These services are usually provided for free in the
        hope that users will make the site their default {home page}
        or at least visit it often.  Popular examples are {Yahoo} and
        {MSN}.  Most portals on the {Internet} exist to generate
        advertising income for their owners, others may be focused on
        a specific group of users and may be part of an {intranet} or
        {extranet}.  Some may just concentrate on one particular
        subject, say technology or medicine, and are known as a
        {vertical portals}.
     
        (2001-07-07)