Knot (noun)

1. A fastening made by looping a piece of string, rope, or something similar on itself and tightening it.
2. A unit of speed used in navigation equal to one nautical mile per hour (1.852 km/h).
3. A hard, knobbly protuberance on a tree trunk or branch.

Origin:

Old english cnotta, of germanic origin; related to dutch knoop and german knoten.

Examples:

1. He tied a knot in the rope.
2. The boat was traveling at 10 knots.
3. The knot in the wood.
4. The knot in the rope was difficult to untie.
5. The knot in the tie.