disassembly has 2 distinct synonyms spread across 1 of its 1 sense. 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 assembly.
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.
the act of taking something apart (as a piece of machinery)
“Russia and the United States discussed the dismantling of their nuclear weapons”
Synonyms, antonyms and the broader and narrower relations for disassembly come from Princeton University’s WordNet. Full sources and licences.