One who starts trouble.
Don't invite that kid to a party, he's a real rable rouser.
An act of speaking more words, usually unnecessary, to fill time and/or set the mood.
Bobby and Will are Rabble Rousers, they won't shut up.
Rabble Rousers at the LA Velodrome tend to enjoy speaking about the ideas of "Rabble Rousers", video games, and Mommy-and-Me Classes.