A square fore-and-aft sail set on the foremast, but behind it, on a schooner or other similar vessel.
The lowest (and usually the largest) square sail hung on the foremast
A triangular sail set forward of the foremast: forestaysail.
In a fore-and-aft-rigged sailing boat, the sail that is set above the gaff at the top part of the mast.
A sail or either of the two sails rigged just above the course sail and supported by the topmast on a square-rigged sailing ship.