ADJECTIVE (3)

1. producing distorted sensory perceptions and feelings or altered states of awareness or sometimes states resembling psychosis;
- Example: "psychedelic drugs like psilocybin and mescaline"

2. having the vivid colors and bizarre patterns associated with psychedelic states;
- Example: "a psychedelic painting"

3. (of a mental state) characterized by intense and distorted perceptions and hallucinations and feelings of euphoria or sometimes despair;
- Example: "a psychedelic experience"

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):

psychedelic
    adj 1: producing distorted sensory perceptions and feelings or
           altered states of awareness or sometimes states
           resembling psychosis; "psychedelic drugs like psilocybin
           and mescaline"
    2: having the vivid colors and bizarre patterns associated with
       psychedelic states; "a psychedelic painting"
    3: (of a mental state) characterized by intense and distorted
       perceptions and hallucinations and feelings of euphoria or
       sometimes despair; "a psychedelic experience"

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "psychedelic":
   DET, DMT, LSD, Mary Jane, STP, THC, acid, antidepressant,
   ataractic, consciousness-expanding, diethyltryptamine,
   dimethyltryptamine, gage, ganja, grass, hallucinational,
   hallucinative, hallucinatory, hallucinogen, hallucinogenic, hash,
   hashish, hay, hemp, joint, kava, marijuana, mescal, mescal bean,
   mescal button, mescaline, mind-altering drug, mind-blowing,
   mind-blowing drug, mind-expanding, mind-expanding drug,
   morning glory seeds, peyote, pot, psilocin, psilocybin,
   psychic energizer, psychoactive drug, psychochemical,
   psychotomimetic, reefer, roach, stick, tea, tranquilizer, weed