The Collaborative International Dictionary of English v.0.48:

Pralltriller \Prall"tril`ler\, n.; G. pl. Prall"triller. [G.]
   (Music)
   A melodic embellishment consisting of the quick alternation
   of a principal tone with an auxiliary tone above it, usually
   the next of the scale; -- called also the inverted
   mordente.
   [Webster 1913 Suppl.] Pram