Source : Webster's Revised Unabridged Dictionary (1913)

Chirp \Chirp\, v. i. [imp. & p. p. {Chirped}; p. pr. & vb. n.
   {Chirping}.] [Of imitative orgin. Cf. {Chirk}, {Chipper},
   {Cheep}, {Chirm}, {Chirrup}.]
   To make a shop, sharp, cheerful, as of small birds or
   crickets.

Chirp \Chirp\, n.
   A short, sharp note, as of a bird or insect. ``The chirp of
   flitting bird.'' --Bryant.

Source : WordNet®

chirp
     n : a sharp sound made by small birds or insects
     v 1: make high-pitched sounds; of birds [syn: {peep}, {twirp}, {cheep},
           {chirrup}]
     2: sing in modulation [syn: {tweedle}]