Merlon
[mur-luhn]
Etymology: French, from Italian merlone, augmentative of merlo battlement, from Medieval Latin merulus, from Latin, merle

1) Part of a battlement, the square “sawtooth” between crenels.
(Gies, Joseph and Francis. Life in a Medieval Castle, 226)

2) Solid part of embattled parapet between embrasures, sometimes pierced with slit.
(Wood, Margaret. The English Medieval House, 413)

*term definitions retrieved from Netserf’s Medieval Glossary (http://www.netserf.org/Glossary)