mainsail

1.bend a mainsail onto the boom.

把主系在杆上

2.reefing the mainsail in strong winds.

在强风中收缩主。

3.Jibe: To shift the mainsail from one side to the other when sailing with the wind behind; also "gybe".

：顺风行驶时将主从的一侧到另一侧。