From The Collaborative International Dictionary of English v.0.48:
Sleepy \Sleep"y\, a. [Compar. Sleepier; superl. Sleepiest.]
[AS. sl?pig. See Sleep, n.]
1. Drowsy; inclined to, or overcome by, sleep. --Shak.
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She waked her sleepy crew. --Dryden.
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2. Tending to induce sleep; soporiferous; somniferous; as, a
sleepy drink or potion. --Chaucer.
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3. Dull; lazy; heavy; sluggish. --Shak.
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'Tis not sleepy business;
But must be looked to speedily and strongly. --Shak.
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4. Characterized by an absence of watchfulness; as, sleepy
security.
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Sleepy duck (Zool.), the ruddy duck.
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