名詞 mainsail:

1. the lowermost sail on the mainmast

main.sail

n.Nautical （名詞）【航?！?/i>
The principal sail of a vessel.
主帆：船舶主要的帆
A quadrilateral or triangular sail set from the after part of the mainmast on a fore-and-aft rigged vessel.
主帆：在船頭船尾都裝有帆的帆船上裝在桅后部的呈四角形或三角形的帆
A square sail set from the main yard on a square-rigged vessel.
主帆：橫帆式帆船上從主桅裝上的方形帆