: a sail set forward of the foremast.

What's a headsail?

1. headsail - any sail set forward of the foremast of a vessel. sail, canvass, canvas, sheet - a large piece of fabric (usually canvas fabric) by means of which wind is used to propel a sailing vessel.

What is a staysail on a sailboat?

A staysail ("stays'l") is a fore-and-aft rigged sail whose luff can be affixed to a stay running forward (and most often but not always downwards) from a mast to the deck, the bowsprit, or to another mast (the mast is item 13 in the illustration right).