knot has 8 distinct synonyms spread across 4 of its 10 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is unknot.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a tight cluster of people or things
“a small knot of women listened to his sermon”
any of various fastenings formed by looping and tying a rope (or cord) upon itself or to another rope or to another object
Synonyms, antonyms and the broader and narrower relations for knot come from Princeton University’s WordNet. Full sources and licences.
a hard cross-grained round piece of wood in a board where a branch emerged
“the saw buckled when it hit a knot”
(of ships and wind) a unit of speed equal to one nautical mile per hour or about 1.15 statute miles per hour
something twisted and tight and swollen
“their muscles stood out in knots”
a sandpiper that breeds in the Arctic and winters in the southern hemisphere
make into knots; make knots out of
“She knotted her fingers”
tie or fasten into a knot
“knot the shoelaces”