Source : Webster's Revised Unabridged Dictionary (1913)

Pralltriller \Prall"tril`ler\, n.; G. pl. {-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}.