The Collaborative International Dictionary of English v.0.48:

Visionary \Vi"sion*a*ry\, a. [Cf. F. visionnaire.]
   1. Of or pertaining to a visions or visions; characterized
      by, appropriate to, or favorable for, visions.
      [1913 Webster]

            The visionary hour
            When musing midnight reigns.          --Thomson.
      [1913 Webster]

   2. Affected by phantoms; disposed to receive impressions on
      the imagination; given to reverie; apt to receive, and act
      upon, fancies as if they were realities.
      [1913 Webster]

            Or lull to rest the visionary maid.   --Pope.
      [1913 Webster]

   3. Existing in imagination only; not real; fanciful;
      imaginary; having no solid foundation; as, visionary
      prospect; a visionary scheme or project. --Swift.
      [1913 Webster]

   Syn: Fanciful; fantastic; unreal. See Fanciful.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Visionary \Vi"sion*a*ry\, n.; pl. Visionaries.
   1. One whose imagination is disturbed; one who sees visions
      or phantoms.
      [1913 Webster]

   2. One whose imagination overpowers his reason and controls
      his judgment; an unpractical schemer; one who builds
      castles in the air; a daydreamer.
      [1913 Webster]

WordNet (r) 3.0 (2006):

visionary
    adj 1: not practical or realizable; speculative; "airy theories
           about socioeconomic improvement"; "visionary schemes for
           getting rich" [syn: airy, impractical, visionary,
           Laputan, windy]
    n 1: a person given to fanciful speculations and enthusiasms
         with little regard for what is actually possible
    2: a person with unusual powers of foresight [syn: visionary,
       illusionist, seer]

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "visionary":
   Barmecidal, Barmecide, Don Quixote, Quixote, Utopian, abstracted,
   addict, airy, apparent, apparitional, astral, autistic, bug,
   chimeric, collector, daydreamer, daydreaming, daydreamy, deceptive,
   delusional, delusionary, delusive, delusory, demon, dereistic,
   dreamer, dreamer of dreams, dreamlike, dreamy, eager beaver,
   energumen, enthusiast, erroneous, escapist, exalted, faddist,
   fallacious, false, fanatic, fanciful, fantast, fantastic, fiend,
   freak, grandiose, great one for, hobbyist, hound, idealist,
   idealistic, illusional, illusionary, illusive, illusory, imaginary,
   impractical, in the clouds, infatuate, introspective, lofty,
   lotus-eater, misleading, musing, noble, nut, ostensible,
   otherworldly, phantasmagoric, phantasmal, phantom, poetic,
   pretentious, prophet, pursuer, quixotic, radical, rhapsodist,
   romancer, romancing, romantic, romanticist, romanticized, seeming,
   seer, self-deceptive, self-deluding, specious, spectral,
   speculative, starry-eyed, storybook, sucker for, supposititious,
   transcendental, transmundane, unactual, unfounded, unpractical,
   unreal, unrealistic, unsubstantial, unworkable, unworldly, utopian,
   utopianist, utopianizer, wish-fulfilling, wishful thinker,
   zealot



The Jargon File (version 4.4.7, 29 Dec 2003):

visionary
 n.

    1. One who hacks vision, in the sense of an Artificial Intelligence
    researcher working on the problem of getting computers to ?see? things
    using TV cameras. (There isn't any problem in sending information from a TV
    camera to a computer. The problem is, how can the computer be programmed to
    make use of the camera information? See SMOP, AI-complete.)

    2. [IBM] One who reads the outside literature. At IBM, apparently, such a
    penchant is viewed with awe and wonder.


The Free On-line Dictionary of Computing (30 December 2018):

visionary

   1. One who hacks vision, in the sense of an Artificial
   Intelligence researcher working on the problem of getting
   computers to "see" things using TV cameras.  (There isn't any
   problem in sending information from a TV camera to a computer.
   The problem is, how can the computer be programmed to make use
   of the camera information?  See SMOP, AI-complete.)

   2. [IBM] One who reads the outside literature.  At IBM,
   apparently, such a penchant is viewed with awe and wonder.

   [Jargon File]