Moonraker (sail)

A moonraker, also known as a moonsail, hope-in-heaven, or hopesail, is a square sail flown immediately above a skysail (see sail-plan) on the royal masts of a square rigged sailing ship. None of the four- and five-masted square rigged ships carried a moonsail.
The equivalent sail, if triangular, is called a skyscraper.
Moonrakers are relatively unusual sails only used on ships built primarily for speed.