Source : Webster's Revised Unabridged Dictionary (1913)

Cardinal \Car"di*nal\, a. [L. cardinalis, fr. cardo the hinge of
   a door, that on which a thing turns or depends: cf. F.
   cardinal.]
   Of fundamental importance; pre["e]minent; superior; chief;
   principal.

         The cardinal intersections of the zodiac. --Sir T.
                                                  Browne.

         Impudence is now a cardinal virtue.      --Drayton.

         But cardinal sins, and hollow hearts, I fear ye.
                                                  --Shak.

   {Cardinal numbers}, the numbers one, two, three, etc., in
      distinction from first, second, third, etc., which are
      called {ordinal numbers}.

   {Cardinal points}
   (a) (Geol.) The four principal points of the compass, or
       intersections of the horizon with the meridian and the
       prime vertical circle, north, south east, and west.
   (b) (Astrol.) The rising and setting of the sun, the zenith
       and nadir.

   {Cardinal signs} (Astron.) Aries, Libra, Cancer, and
      Capricorn.

   {Cardinal teeth} (Zo["o]l.), the central teeth of bivalve
      shell. See {Bivalve}.

   {Cardinal veins} (Anat.), the veins in vertebrate embryos,
      which run each side of the vertebral column and returm the
      blood to the heart. They remain through life in some
      fishes.

   {Cardinal virtues}, pre["e]minent virtues; among the
      ancients, prudence, justice, temperance, and fortitude.

   {Cardinal winds}, winds which blow from the cardinal points
      due north, south, east, or west.

Cardinal \Car"di*nal\, n. [F. carinal, It. cardinale, LL.
   cardinalis (ecclesi[ae] Roman[ae]). See {Cardinal}, a.]
   1. (R. C. Ch.) One of the ecclesiastical princes who
      constitute the pope's council, or the sacred college.

            The clerics of the supreme Chair are called
            Cardinals, as undoubtedly adhering more nearly to
            the hinge by which all things are moved. --Pope Leo
                                                  IX.

   Note: The cardinals are appointed by the pope. Since the time
         of Sixtus V., their number can never exceed seventy
         (six of episcopal rank, fifty priests, fourteen
         deacons), and the number of cardinal priests and
         deacons is seldom full. When the papel chair is vacant
         a pope is elected by the college of cardinals from
         among themselves. The cardinals take precedence of all
         dignitaries except the pope. The principal parts of a
         cardinal's costume are a red cassock, a rochet, a short
         purple mantle, and a red hat with a small crown and
         broad brim, with cords and tessels of a special pattern
         hanging from it.

   2. A woman's short cloak with a hood.

            Where's your cardinal! Make haste.    --Lloyd.

   3. Mulled red wine. --Hotten.

Source : WordNet®

cardinal
     n 1: (Roman Catholic Church) one of a group of more than 100
          prominent bishops in the Sacred College who advise the
          Pope and elect new Popes
     2: the number of elements in a mathematical set; denotes a
        quantity but not the order [syn: {cardinal number}]
     3: a variable color averaging a vivid red [syn: {carmine}]
     4: crested thick-billed North American finch having bright red
        plumage in the male [syn: {cardinal grosbeak}, {Richmondena
        Cardinalis}, {Cardinalis cardinalis}, {redbird}]

cardinal
     adj 1: serving as an essential component; "a cardinal rule"; "the
            central cause of the problem"; "an example that was
            fundamental to the argument"; "computers are
            fundamental to modern industrial structure" [syn: {central},
             {fundamental}, {key}, {primal}]
     2: being or denoting a numerical quantity but not order;
        "cardinal numbers" [ant: {ordinal}]