Rare literary term for a shaven head, especially in a Buddhist monastic context. In modern Japanese, 剃髪 (ていはつ) or 坊主頭 (ぼうずあたま) are more common.
In old documents, the tonsure of monks is described.
From Chinese 圓顱 (yuánlú), literally 'round skull', referring to a shaven head. The exact historical derivation in Japanese is uncertain; it is a literary borrowing.