The Collaborative International Dictionary of English v.0.48:

dreamy \dream"y\ (dr[=e]m"[y^]), a. [Compar. Dreamier
   (dr[=e]m"[i^]*[~e]r); superl. Dreamiest.]
   1. Abounding in dreams or given to dreaming; appropriate to,
      or like, dreams; visionary. "The dreamy dells."
      --Tennyson.
      [1913 Webster]

   2. soothing; restful; as, dreamy music.
      [PJC]

   3. Like what one dreams of; wonderful; delightful; marvelous;
      ideal; as, a dreamy house and garden. [informal]
      [PJC]

   4. Prone to indulge in fantasy or daydreaming; as, a dreamy
      young girl.
      [PJC]

WordNet (r) 3.0 (2006):

dreamy
    adj 1: dreamy in mood or nature; "a woolgathering moment" [syn:
           dreamy, moony, woolgathering]
    2: lacking spirit or liveliness; "a lackadaisical attempt"; "a
       languid mood"; "a languid wave of the hand"; "a hot
       languorous afternoon" [syn: dreamy, lackadaisical,
       languid, languorous]

Moby Thesaurus II by Grady Ward, 1.0:

174 Moby Thesaurus words for "dreamy":
   Barmecidal, Barmecide, absent, absent-minded, absentminded,
   absorbed, abstracted, airy, anesthetized, apparent, apparitional,
   appeasing, astral, autistic, bemused, calming, castle-building,
   cataleptic, charmed, chimeric, comatose, cool, cradling, dandy,
   daydreaming, daydreamy, deceptive, delusional, delusionary,
   delusive, delusory, dereistic, divine, doped, dozy, dreamful,
   dreaming, dreamlike, dreamy-eyed, dreamy-souled, drowsing, drowsy,
   drugged, drugged with sleep, ecstatic, elsewhere, enchanted,
   engrossed, entranced, erroneous, faint, fallacious, false,
   fanciful, fantastic, faraway, gentle, gentling, glorious, groovy,
   half asleep, half-awake, heavy, heavy with sleep, heavy-eyed,
   hushing, idealistic, illusional, illusionary, illusive, illusory,
   imaginary, in a reverie, in a stupor, in a trance, in the clouds,
   indefinite, indistinct, intangible, languid, lazy, lethargic, lost,
   lost in thought, lulling, meditative, misleading, misty,
   mollifying, mooning, moonraking, museful, musing, napping,
   narcoleptic, narcose, narcotized, narcous, neat, nifty, nodding,
   oblivious, occupied, oscitant, ostensible, otherworldly, out of it,
   pacifying, peaceable, peaceful, peachy, pensive, phantasmagoric,
   phantasmal, phantom, pipe-dreaming, preoccupied, quiet, quietening,
   rapt, relaxing, restful, rocking, romantic, sedated, seeming,
   self-deceptive, self-deluding, shadowy, sleep-drowned, sleep-drunk,
   sleep-filled, sleep-swollen, sleepful, sleepy, slumberous,
   slumbery, snoozy, somewhere else, somnolent, soothful, soothing,
   soporific, specious, spectral, spellbound, spelled, stargazing,
   stilling, stretchy, stuporose, stuporous, super, supposititious,
   taken up, thoughtful, tranced, tranquil, tranquilizing,
   transported, unactual, unconscious, undefined, unfounded, unreal,
   unsubstantial, unworldly, vague, visionary, whimsical,
   woolgathering, wrapped in thought, yawning, yawny