The Collaborative International Dictionary of English v.0.48:

Peep \Peep\ (p[=e]p), n.
   1. The cry of a young chicken; a chirp.
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   2. First outlook or appearance.
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            Oft have we seen him at the peep of dawn. --Gray.
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   3. A sly look; a look as through a crevice, or from a place
      of concealment.
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            To take t' other peep at the stars.   --Swift.
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   4. (Zool.)
      (a) Any small sandpiper, as the least sandpiper (Trigna
          minutilla).
      (b) The European meadow pipit (Anthus pratensis).
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   Peep show, a small show, or object exhibited, which is
      viewed through an orifice or a magnifying glass.

   Peep-o'-day boys, the Irish insurgents of 1784; -- so
      called from their visiting the house of the loyal Irish at
      day break in search of arms. [Cant]
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The Collaborative International Dictionary of English v.0.48:

Peep \Peep\ (p[=e]p), v. i. [imp. & p. p. Peeped (p[=e]pt); p.
   pr. & vb. n. Peeping.] [Of imitative origin; cf. OE. pipen,
   F. piper, p['e]pier, L. pipire, pipare, pipiare, D. & G.
   piepen. Senses 2 and 3 perhaps come from a transfer of sense
   from the sound which chickens make upon the first breaking of
   the shell to the act accompanying it; or perhaps from the
   influence of peek, or peak. Cf. Pipe.]
   1. To cry, as a chicken hatching or newly hatched; to chirp;
      to cheep.
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            There was none that moved the wing, or opened the
            mouth, or peeped.                     --Is. x. 14.
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   2. To begin to appear; to look forth from concealment; to
      make the first appearance; as, the sun peeped over the
      eastern hills.
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            When flowers first peeped, and trees did blossoms
            bear.                                 --Dryden.
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   3. To look cautiously or slyly; to peer, as through a
      crevice; to pry.
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            Peep through the blanket of the dark. --Shak.
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            From her cabined loophole peep.       --Milton.
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   Peep sight, an adjustable piece, pierced with a small hole
      to peep through in aiming, attached to a rifle or other
      firearm near the breech.
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WordNet (r) 3.0 (2006):

peep
    n 1: the short weak cry of a young bird [syn: cheep, peep]
    2: a secret look [syn: peek, peep]
    v 1: look furtively; "He peeped at the woman through the window"
    2: cause to appear; "he peeped his head through the window"
    3: make high-pitched sounds; "the birds were chirping in the
       bushes" [syn: peep, cheep, chirp, chirrup]
    4: speak in a hesitant and high-pitched tone of voice
    5: appear as though from hiding; "the new moon peeped through
       the tree tops"