The Collaborative International Dictionary of English v.0.48:

Patter \Pat"ter\, v. t.
   1. To spatter; to sprinkle. [R.] "And patter the water about
      the boat." --J. R. Drake.
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   2. [See Patter, v. i., 2.] To mutter; as prayers.
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            [The hooded clouds] patter their doleful prayers.
                                                  --Longfellow.
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   To patter flash, to talk in thieves' cant. [Slang]
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The Collaborative International Dictionary of English v.0.48:

Patter \Pat"ter\, n.
   1. A quick succession of slight sounds; as, the patter of
      rain; the patter of little feet.
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   2. Glib and rapid speech; a voluble harangue.
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   3. The cant of a class; patois; as, thieves's patter;
      gypsies' patter.
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   4. The language or oratory of a street peddler, conjurer, or
      the like, hence, glib talk; a voluble harangue; mere talk;
      chatter; also, specif., rapid speech, esp. as sometimes
      introduced in songs. [Cant or Colloq.]
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Patter \Pat"ter\, v. i. [imp. & p. p. Pattered; p. pr. & vb.
   n. Pattering.] [Freq. of pat to strike gently.]
   1. To strike with a quick succession of slight, sharp sounds;
      as, pattering rain or hail; pattering feet.
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            The stealing shower is scarce to patter heard.
                                                  --Thomson.
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   2. To mutter; to mumble; as, to patter with the lips.
      --Tyndale. [In this sense, and in the following, perh.
      from paternoster.]
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   3. To talk glibly; to chatter; to harangue. [Colloq.]
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            I've gone out and pattered to get money. --Mayhew.
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WordNet (r) 3.0 (2006):

patter
    n 1: plausible glib talk (especially useful to a salesperson)
         [syn: spiel, patter, line of gab]
    2: a quick succession of light rapid sounds; "the patter of
       mice"; "the patter of tiny feet"
    v 1: rain gently; "It has only sprinkled, but the roads are
         slick" [syn: sprinkle, spit, spatter, patter,
         pitter-patter]
    2: make light, rapid and repeated sounds; "gently pattering
       rain" [syn: patter, pitter-patter]