noun, noun or participle which takes 'suru'
Refers to the act of cutting off a head, often in historical or execution contexts. Can be used as a noun or with する.
中世では斬首が公開処刑の一つだった。
In the Middle Ages, beheading was one form of public execution.
The criminal was decapitated.
noun
decapitated head; severed head
Refers to the head that has been cut off. Less common than the act sense.
戦場には斬首が転がっていた。
Decapitated heads lay scattered on the battlefield.