n. 大桅的帆, 主帆

[ noun ]
the lowermost sail on the mainmast
<noun.artifact>

Mainsail \Main"sail`\ (m[=a]n"s[=a]l`), n. (Naut.)
The principal sail in a ship or other vessel.

[They] hoised up the mainsail to the wind. -- Acts
xxvii. 40.

Note: The mainsail of a ship is extended upon a yard attached
to the mainmast, and that of a sloop or schooner upon
the boom.