bowline knot

noun

1. a rope running forward from the middle of a square sail's weather edge to the bow, used to keep the sail taut when the ship is sailing into the wind
2. a knot used in making a loop that will not slip or tighten under tension
   in full bowline knot: see knot,

Origin: ME boueline, prob. < MDu boeglijne (or Dan bovline); for IE bases see bow & line