BACKING the Sails, in Navigation: to arrange them in a situation that will force the ship to retreat, or move backwards. This is, however, only done in narrow channels, when a ship is carried along sidewise by the tide or current, and wants to avoid any thing that may interrupt her progress, as shoals, vessels at anchor, &c. or in the line of battle, when a ship wants to be immediately opposite to another with which she is engaged.