Definitions of patter:

• noun:   a quick succession of light rapid sounds

  Example: "The patter of mice"

• noun:   plausible glib talk (especially useful to a salesperson)
• verb:   make light, rapid and repeated sounds

  Example: "Gently pattering rain"

• verb:   rain gently
• name:  A surname (very rare: popularity rank in the U.S.: #55024)