Source : Webster's Revised Unabridged Dictionary (1913)

Pitter-patter \Pit"ter-pat`ter\, n.
   A sound like that of alternating light beats. Also, a
   pattering of words.

Pitter-patter \Pit"ter-pat`ter\, adv.
   With, or with the sound of, alternating light beats; as, his
   heart went pitter-patter.

Source : WordNet®

pitter-patter
     n : a series of rapid tapping sounds; "she missed the
         pitter-patter of little feet around the house"
     adv 1: as of footsteps; "he came running pit-a-pat down the hall"
            [syn: {pit-a-pat}, {pitty-patty}, {pitty-pat}]
     2: describing a rhythmic beating; "his heart went pit-a-pat"
        [syn: {pit-a-pat}, {pitty-patty}, {pitty-pat}]
     v 1: rain gently; "It has only sprinkled, but the roads are
          slick" [syn: {sprinkle}, {spit}, {spatter}, {patter}]
     2: make light, rapid and repeated sounds; "gently pattering
        rain" [syn: {patter}]