A unique, large sail used during
racing. I can only describe it as looking like a
parachute, only
triangular, though the opposite of a
drag chute. It has an enormous amount of
surface area to grab the
wind. Very
colorful and
beautiful.
The spinnaker is controlled by two "sheets" (for you landlubbers, the rope to pull in the sail), but the sheet which is led by the spinnaker pole is called the guy and is attached to the windward clew of the spinnaker. The sheet is attached to the leeward clew. The positions reverse when the spinnaker is gybed.
The spinnaker pole is attached to the spinnaker via the guy. The pole must have an uphaul and downhaul atatched to keep the pole horizontal.
Both sheet and guy are led through blocks on the aft deck and on to the winches, usually a dedicated one.
For some pictures, check out:
http://www.dedekam.com/sdetail1.html
http://www.dedekam.com/sdetail4.html