the foremost sail of a ship, being a large staysail extended from the outer end of the bowsprit prolonged by the jib-boom, towards the fore-top mast head. See SAIL.

The jib is a sail of great command with any side-wind, but especially when the ship is close hauled, or has the wind upon her beam; and its effort in caulking the ship, or turning her head to leeward, is very powerful and of great utility, particularly when the ship is working through a narrow channel.

JIB-Boom, a boom run out from the extremity of the bowsprit, parallel to its length, and serving to extend the bottom of the jib, and the stay of the fore-top-gallant mast. This boom, which is nothing more than a continuation of the bowsprit forward, to which it may be considered as a top-mast, is usually attached to the bowsprit, by means of two large boom-irons, or by one boom-iron, and a cap on the outer end of the bowsprit; or, finally, by the cap without and a strong lashing within, instead of a boom-iron, which is generally the method of securing it in small merchant ships. It may therefore be drawn in upon the bowsprit as occasion requires; which is usually practised when the ship enters a harbour, where it might very soon be broken or carried away, by the vessels which are moored therein, or passing by under sail.