The act of gybing.

(by extension) A sudden change in approach or direction; vacillation.

To shift a fore-and-aft sail from one side of a sailing vessel to the other, while sailing before the wind.

Of a fore-and-aft sail or its boom: to shift, often forcefully and suddenly, from one side of a sailing vessel to the other.

Generally of a small sailing vessel: to change tack with the wind crossing behind the vessel.