BisbigliandoBisbigliando ("whispering" in Italian) is a special tremolo effect on the harp where a chord or note is rapidly repeated at a low volume. Usually, the effect is achieved by both hands playing adjecent strings set to the same pitcheses. This is possible because of enharmonic spellings created by the pedals. It can sound like strumming a guitar or even "watery".
On sheet music, it is represented by three thick lines connecting the notes to be trilled.