Stunsail
A stunsail was an extra sail that was attached to the yardarm of a sailing vessel.

During the promotion of Worf aboard the holodeck recreation of the 19th century  , when asked by Geordi La Forge, what a stunsail was after he was order to set them, Commander William T. Riker pointed out that it was the sail located just above the last yardarm. ()

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Propulsion technology