n A looping of a piece of string or of any other long, flexible material that cannot be untangled without passing one or both ends of the material through its loops.
n (mathematics) A non-self-intersecting closed curve in (e.g., three-dimensional) space that is an abstraction of a knot (in sense 1 above).
n One of a variety shore bird; the red-breasted sandpiper (variously Calidris canutus or (taxlink|Tringa canutus|species)).