Source : Webster's Revised Unabridged Dictionary (1913)

Pitapat \Pit"a*pat`\, adv. [An onomatopoetic reduplication of
   pat a light, quick blow.]
   In a flutter; with palpitation or quick succession of beats.
   --Lowell. ``The fox's heart went pitapat.'' --L'Estrange.

Pitapat \Pit"a*pat`\, n.
   A light, repeated sound; a pattering, as of the rain. ``The
   pitapat of a pretty foot.'' --Dryden.