circular window; round window
A window that is circular in shape, often found in traditional Japanese architecture, ships, or modern design.
The garden can be seen through the circular window of the tea room.
船の丸窓から海を眺めた。
I looked out at the sea through the ship's round window.
Standard kanji spelling; 丸 means 'round' and 窓 means 'window'.
Alternate kanji spelling using 円 (circle/round); less common than 丸窓 but still used.
Compound of 丸 (maru, 'round') + 窓 (mado, 'window'). The alternate spelling 円窓 uses 円 (en/maru, 'circle') for the same meaning.