Daily entries from the 17th century London diary
Dictionary.com defines it as:
A conventicle is a small, unofficial and unofficiated meeting of laypeople, to discuss religious issues in a non-threatening, intimate manner. Philipp Jakob Spener called for such associations in his Pia Desideria, and they were the foundation of the German Evangelical Lutheran Pietist movement. Due to concern over possibly mixed-gender meetings, sexual impropriety, and subversive sectarianism conventicles were condemned first by mainstream Lutheranism and then by the Pietists within decades of their inception. In Finland conventicle has remained the base activity especially in the Finnish Awakening revivalist movement. Today, the cell groups used in some churches are similar.
English Dissenters religious and social, by sect, prior to, during and after the Civil War:-