noun
vault of heaven; vaulted sky
Poetic or literary term for the sky as a vast dome or arch. Rare in everyday conversation; found in classical or descriptive writing.
夜空を見上げると、穹窿に無数の星が輝いていた。
Looking up at the night sky, countless stars shone in the vault of heaven.
noun
Architectural sense: a dome or arched vault. Also rare and literary; modern technical terms like ドーム or アーチ are more common.
教会の穹窿には美しいフレスコ画が描かれている。
Beautiful frescoes are painted on the vault of the church.
From Chinese 穹窿 (qiónglóng), meaning 'dome' or 'vault'. The kanji 穹 means 'sky' or 'vault', and 窿 means 'dome' or 'arch'. The exact historical derivation is uncertain; the spelling is conventionally associated with these meanings.