This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. The principal sail of a vessel.

n. A quadrilateral or triangular sail set from the after part of the mainmast on a fore-and-aft rigged vessel.

n. A square sail set from the main yard on a square-rigged vessel.

n. The largest (or only) sail on a sailing vessel.

n. The principal sail in a ship or other vessel.

n. In a square-rigged vessel, the sail bent to the main-yard; the main course: in a fore-and-aft rigged vessel, the large sail set on the after part of the mainmast.

n. plural The square sails on the mainmast: they are the course, or mainsail proper, the lower and upper topsails, the topgallantsail and royal, and also a skysail if the ship is lofty. Men-of-war usually carry single topsails instead of a divided sail.

n. the lowermost sail on the mainmast

"One model, of a full-rigged ship, twenty-five feet in length, with skysail yards and all sails set, precise in every minutest detail aloft and alow, was undamaged save for a rent in her mainsail from a fragment of shell."

canvass    canvas    sail    sheet   

mainsail haul!   

main course   

foresail    spanker    main-topsail    topsail    staysail