dissimilate has no recorded synonym. 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 assimilate.
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.
become dissimilar by changing the sound qualities
“These consonants dissimilate”
make dissimilar; cause to become less similar
become dissimilar or less similar
“These two related tribes of people gradually dissimilated over time”
Synonyms, antonyms and the broader and narrower relations for dissimilate come from Princeton University’s WordNet. Full sources and licences.