Knot

1. A tight cluster of people or things. A small knot of women listened to his sermon.
2. Any of various fastenings formed by looping and tying a rope (or cord) upon itself or to another rope or to another object. He secured the boat with a knot on the rope.
3. A hard cross-grained round piece of wood in a board where a branch emerged. A board with a knot can cause a problem.
4. Something twisted and tight and swollen. Their muscles stood out in knots.
5. A unit of length used in navigation; equivalent to the distance spanned by one minute of arc in latitude; 1,852 meters. A destroyer can make almost 40 knots an hour.