noun
Literary or historical term for cutting off the head. Often appears in the set phrase 刎頸の交わり (friendship so deep one would risk decapitation for the other).
「刎頸の交わり」という言葉は、命を懸けた友情を表す。
The phrase 刎頸の交わり expresses a friendship for which one would risk one's life.
斬首 is a more common and neutral term for decapitation, while 刎頸 is literary and strongly associated with the classical friendship idiom.
The exact derivation is uncertain; the kanji 刎 (cut off) and 頸 (neck) combine to mean 'cutting the neck'. The term is preserved mainly through the classical Chinese-derived idiom 刎頸の交わり.