English: voussoir
Welsh: carreg fwa
Subject: Ystadau a Cadw
English definition: A shaped brick or piece of stone forming part of an arch. 
Welsh definition: Bricsen neu ddarn o faen wedi ei siapio i ffurfio rhan o fwa.
Welsh context: Ffynhonnell: Taflen wybodaeth gyhoeddus Cyngor Gwynedd.