Noun

1. A tight cluster of people or things
2. Any of various fastenings formed by looping and tying a rope (or cord) upon itself or to another rope or to another object
3. A hard cross-grained round piece of wood in a board where a branch emerged
4. Something twisted and tight and swollen
5. A unit of length used in navigation; exactly 1,852 meters; historically based on the distance spanned by one minute of arc in latitude
6. Soft lump or unevenness in a yarn; either an imperfection or created by design
7. A sandpiper that breeds in the arctic and winters in the southern hemisphere

Verb

1. Make into knots; make knots out of
2. Tie or fasten into a knot
3. Tangle or complicate