tummler

n.

1. One, such as a social director or entertainer, who encourages guest or audience participation.
2. One who incites others to action.

[Yiddish tumler, from tumlen, to make a racket.]

[fr. Yiddish tumler]  /TOOM ler/  
1) one, such as a social director or entertainer, who encourages guest or audience participation
2) one who incites others to action