Wordnet 3.0
NOUN (1)
1. 
 a transparent purple variety of quartz; 
 used as a gemstone; 
ADJECTIVE (1)
1. 
 of a moderate purple color; 
The Collaborative International Dictionary of English v.0.48:
Amethyst \Am"e*thyst\, [F. ametiste, amatiste, F. am['e]thyste,
   L. amethystus, fr. Gr. ? without drunkenness; as a noun, a
   remedy for drunkenness, the amethyst, supposed to have this
   power; 'a priv. + ? to be drunken, ? strong drink, wine. See
   Mead.]
   [1913 Webster]
   1. (Min.) A variety of crystallized quartz, of a purple or
      bluish violet color, of different shades. It is much used
      as a jeweler's stone.
      [1913 Webster]
   Oriental amethyst, the violet-blue variety of transparent
      crystallized corundum or sapphire.
      [1913 Webster]
   2. (Her.) A purple color in a nobleman's escutcheon, or coat
      of arms.
      [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
colorful \colorful\ adj.
   1. having striking color. Opposite of colorless.
   Note: [Narrower terms: changeable, chatoyant, iridescent,
         shot; deep, rich; flaming; fluorescent, glowing;
         prismatic; psychedelic; red, ruddy, flushed,
         empurpled]
   Syn: colourful.
        [WordNet 1.5]
   2. striking in variety and interest. Opposite of colorless
      or dull. [Narrower terms: brave, fine, gay, glorious;
      flamboyant, resplendent, unrestrained; flashy, gaudy,
      jazzy, showy, snazzy, sporty; picturesque]
      [WordNet 1.5]
   3. having color or a certain color; not black, white or grey;
      as, colored crepe paper. Opposite of colorless and
      monochrome.
   Note: [Narrower terms: tinted; touched, tinged; amber,
         brownish-yellow, yellow-brown; amethyst; auburn,
         reddish-brown; aureate, gilded, gilt, gold, golden;
         azure, cerulean, sky-blue, bright blue; bicolor,
         bicolour, bicolored, bicoloured, bichrome; blue,
         bluish, light-blue, dark-blue; blushful,
         blush-colored, rosy; bottle-green; bronze, bronzy;
         brown, brownish, dark-brown; buff; canary,
         canary-yellow; caramel, caramel brown; carnation;
         chartreuse; chestnut; dun; earth-colored,
         earthlike; fuscous; green, greenish, light-green,
         dark-green; jade, jade-green; khaki; lavender,
         lilac; mauve; moss green, mosstone; motley,
         multicolor, culticolour, multicolored, multicoloured,
         painted, particolored, particoloured, piebald, pied,
         varicolored, varicoloured; mousy, mouse-colored;
         ocher, ochre; olive-brown; olive-drab; olive;
         orange, orangish; peacock-blue; pink, pinkish;
         purple, violet, purplish; red, blood-red, carmine,
         cerise, cherry, cherry-red, crimson, ruby, ruby-red,
         scarlet; red, reddish; rose, roseate; rose-red;
         rust, rusty, rust-colored; snuff, snuff-brown,
         snuff-color, snuff-colour, snuff-colored,
         snuff-coloured, mummy-brown, chukker-brown; sorrel,
         brownish-orange; stone, stone-gray; straw-color,
         straw-colored, straw-coloured; tan; tangerine;
         tawny; ultramarine; umber; vermilion,
         vermillion, cinibar, Chinese-red; yellow, yellowish;
         yellow-green; avocado; bay; beige; blae
         bluish-black or gray-blue); coral; creamy; cress
         green, cresson, watercress; hazel; honey,
         honey-colored; hued(postnominal); magenta;
         maroon; pea-green; russet; sage, sage-green;
         sea-green] [Also See: chromatic, colored, dark,
         light.]
   Syn: colored, coloured, in color(predicate).
        [WordNet 1.5]
WordNet (r) 3.0 (2006):
amethyst
    adj 1: of a moderate purple color
    n 1: a transparent purple variety of quartz; used as a gemstone
Easton's 1897 Bible Dictionary:
Amethyst
   one of the precious stones in the breastplate of the high priest
   (Ex. 28:19; 39:12), and in the foundation of the New Jerusalem
   (Rev. 21:20). The ancients thought that this stone had the power
   of dispelling drunkenness in all who wore or touched it, and
   hence its Greek name formed from _a_, "privative," and _methuo_,
   "to get drunk." Its Jewish name, _ahlamah'_, was derived by the
   rabbins from the Hebrew word _halam_, "to dream," from its
   supposed power of causing the wearer to dream.
     It is a pale-blue crystallized quartz, varying to a dark
   purple blue. It is found in Persia and India, also in different
   parts of Europe.