occlusion has 6 distinct synonyms spread across 3 of its 5 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.
closure or blockage (as of a blood vessel)
(meteorology) a composite front when colder air surrounds a mass of warm air and forces it aloft
(dentistry) the normal spatial relation of the teeth when the jaws are closed
an obstruction in a pipe or tube
“we had to call a plumber to clear out the blockage in the drainpipe”
Synonyms, antonyms and the broader and narrower relations for occlusion come from Princeton University’s WordNet. Full sources and licences.