conventicle

Merriam-Webster's Word of the Day for April 07, 2011 is:

conventicle • \kun-VEN-tih-kul\  • noun
1 : an assembly of an irregular or unlawful character 2 : an assembly for religious worship; especially : a meeting for worship not sanctioned by law 3 : meetinghouse

Examples:
In 18th-century England, it was a capital offense to preach in any conventicle.

The radicals tended to meet in small conventicles, sometimes in houses and farmsteads but also in cellars, gates, wayside shelters, clearings, water towers, forests, meadows, or 'windstill zones,' border areas where jurisdiction was contested. -- From C. Scott Dixon's 2010 book Protestants: A History from Wittenberg to Pennsylvania 1517–1740

Did you know?
Conventicle comes to us from Latin conventiculum and ultimately from convenire, meaning to assemble. Conventiculum means place of assembly (it was applied in particular to Roman Christian meetinghouses) or simply assembly. The English conventicle also originally meant assembly. It then developed an application to illegal meetings, which, in turn, led to the arrival of a sense describing secret meetings for worship in a religion proscribed by law. And finally, conventicle developed a sense of meetinghouse, echoing the earlier use of conventiculum.