Medical Definition of knot
1: an interlacing of the parts of one or more flexible bodies (as threads or sutures) in a lump to prevent their spontaneous separation—see surgeon's knot
2: a usually firm or hard lump, swelling, or protuberance in or on a part of the body or a bone or process <a knot in a gland> <a bone with two or three knots>—compare surfer's knot
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