kanji 'big shell' radical
Refers to the kanji radical 頁 (おおがい), literally 'big shell', which appears in characters related to the head or pages.
'頁' is one of the radicals, called 大貝.
Standard kanji form for the radical name.
The kanji itself, used as a radical name; rarely used as a standalone word with this reading.
The reading おおがい comes from the kanji components 大 (big) and 貝 (shell), describing the shape of the radical 頁.