Source : Webster's Revised Unabridged Dictionary (1913)

Sleepy \Sleep"y\, a. [Compar. {Sleepier}; superl. {Sleepiest}.]
   [AS. sl?pig. See {Sleep}, n.]
   1. Drowsy; inclined to, or overcome by, sleep. --Shak.

            She waked her sleepy crew.            --Dryden.

   2. Tending to induce sleep; soporiferous; somniferous; as, a
      sleepy drink or potion. --Chaucer.

   3. Dull; lazy; heavy; sluggish. --Shak.

            'Tis not sleepy business; But must be looked to
            speedily and strongly.                --Shak.

   4. Characterized by an absence of watchfulness; as, sleepy
      security.

   {Sleepy duck} (Zo["o]l.), the ruddy duck.

Source : WordNet®

sleepy
     adj : ready to fall asleep; "beginning to feel sleepy"; "a
           sleepy-eyed child with drooping eyelids"; "sleepyheaded
           students" [syn: {sleepy-eyed}, {sleepyheaded}]
     [also: {sleepiest}, {sleepier}]

sleepier
     See {sleepy}