cas·​tel·​la·​tion | \ ˌkastəˈlāshən\
plural -s

Definition of castellation

1 : the act of castellating
2 : a castellated structure
3a : battlement
b : a groove or recess in a castellated structure (as a nut) a cotter pin passing through the castellation and the hole in the bolt

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History and Etymology for castellation

Medieval Latin castellation-, castellatio, from castellatus + -ion, -io -ion

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