hedge sermon

noun1

1. •
   (historical) An open-air religious service held by Calvinists in the Low Countries during the Reformation, typically in rural areas beyond the reach of civic authorities.

   • The first so-called hedge sermon was held in the cemetery of Boeschepe in the always turbulent Flemish Westkwartier on Sunday morning, July 12, timed to coincide with mass. — 2008