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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