noun A piece of fabric attached to a boat and arranged such that it causes the wind to drive the boat along. The sail may be attached to the boat via a combination of mast, spars and ropes.
noun The concept of a sail or sails, as if a substance.
Take in sail: a storm is coming.
noun The power harnessed by a sail or sails, or the use of this power for travel or transport.
noun A trip in a boat, especially a sailboat.
Let's go for a sail.
noun A sailing vessel; a vessel of any kind; a craft.
Twenty sail were in sight.
noun The conning tower of a submarine.
noun The blade of a windmill.
noun A tower-like structure found on the dorsal (topside) surface of submarines.