indestructible has 3 distinct synonyms spread across 1 of its 2 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. Its one recorded opposite is destructible.
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.
not easily destroyed
very long lasting
“less durable rocks were gradually worn away to form valleys”
Synonyms, antonyms and the broader and narrower relations for indestructible come from Princeton University’s WordNet. Full sources and licences.