conventicle
noun
[ kənˈvɛntɪk(ə)l ]
• a secret or unlawful religious meeting, typically of nonconformists.
Origin:
late Middle English (in the general sense ‘assembly, meeting’, particularly a clandestine or illegal one): from Latin conventiculum ‘(place of) assembly’, diminutive of conventus ‘assembly, company’, from the verb convenire (see convene).