Sailing Terms That Begin with the letter 'I'
Icing- A serious hazard where cold temperatures (below about -10°C) combined with high wind speed (typically force 8 or above on the Beaufort scale) result in spray blown off the sea freezing immediately on contact with the ship.
Idlers- Members of a ship's company not required to serve watches. These were in general specialist tradesmen such as the carpenter and the sailmaker.
In Irons- When the bow of a sailboat is headed into the wind and the boat has stalled and is unable to maneuver.
In the offing- In the water visible from on board a ship, now used to mean something imminent.
Inboard-Outboard drive system- A larger Power Boating alternative drive system to transom mounted outboard motors.
Sailing Terms That Begin with the letter 'J'
Jack- Either a flag, or a sailor. Typically the flag was talked about as if it were a member of the crew. Strictly speaking, a flag is only a "jack" if it is worn at the jackstaff at the bow of a ship.
Jacklines or Jack Stays- Lines, often steel wire with a - plastic jacket, from the bow to the stern on both port and starboard. The Jack Lines are used to clip on the safety harness to secure the crew to the vessel while giving them the freedom to walk on the deck.
Jack Tar- A sailor dressed in 'square rig' with square collar. Formerly with a tarred pigtail.
Jib- A triangular staysail at the front of a ship.
Jigger-mast- The fourth mast, although ships with four or more masts were uncommon, or the aft most mast where it is smallest on vessels of less than four masts.
Jollies- Traditional Royal Navy nickname for the Royal Marines.
Junk- Old cordage past its useful service life as lines aboard ship. The strands of old junk were teased apart in the process called picking oakum.
Sailing Terms That Begin with the letter 'K'
Killick- A small anchor. A fouled killick is the substantive badge of non-commissioned officers in the RN. Seamen promoted to the first step in the promotion ladder are called "Killick". The badge signifies that here is an Able Seaman skilled to cope with the awkward job of dealing with a fouled anchor.
Keel- The central structural basis of the hull.
Keelhauling- Maritime punishment: to punish by dragging under the keel of a ship.
Kelson- The timber immediately above the keel of a wooden ship.
Kissing the gunner's daughter- bend over the barrel of a gun for punitive spanking with a cane or cat.
Know the ropes- A sailor who 'knows the ropes' is familiar with the miles of cordage and ropes involved in running a ship.