calcify 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 decalcify.
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 inflexible and unchanging
“Old folks can calcify”
turn into lime; become calcified
“The rock calcified over the centuries”
convert into lime
“the salts calcified the rock”
Synonyms, antonyms and the broader and narrower relations for calcify come from Princeton University’s WordNet. Full sources and licences.