Opposed to or destructive of the church or ecclesiastical authority; breaking or rejecting church institutions.
From 'ecclesia' (church) plus Greek 'klastos' meaning 'broken' (from klazein 'to break'). Mirrors 'iconoclastic' but targets churches instead of images.
Ecclesioclastic is the word for church-breakers—just as iconoclasts destroyed religious images, ecclesioclasts attacked church institutions themselves, which is exactly what Protestant reformers were accused of being!
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