knock has 17 distinct synonyms spread across 9 of its 11 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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.
deliver a sharp blow or push
“He knocked the glass clear across the room”
rap with the knuckles
“knock on the door”
find fault with; express criticism of; point out real or perceived flaws
“The paper criticized the new movie”
Synonyms, antonyms and the broader and narrower relations for knock come from Princeton University’s WordNet. Full sources and licences.
a bad experience
“the school of hard knocks”