elastic has 5 distinct synonyms spread across 2 of its 4 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 inelastic.
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.
a narrow band of elastic rubber used to hold things (such as papers) together
a fabric made of yarns containing an elastic material
capable of resuming original shape after stretching or compression; springy
“an elastic band”
Synonyms, antonyms and the broader and narrower relations for elastic come from Princeton University’s WordNet. Full sources and licences.