Open English Wordnet
Nouns
(n)pitter-pattera series of rapid tapping sounds“she missed the pitter-patter of little feet around the house”
Verbs
Adverbs
(r)pit-a-pat, pitty-patty, pitty-pat, pitter-patteras of footsteps“he came running pit-a-pat down the hall”
(r)pit-a-pat, pitty-patty, pitty-pat, pitter-patterdescribing a rhythmic beating“his heart went pit-a-pat”