compress has 6 distinct synonyms spread across 2 of its 3 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 decompress.
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.
make more compact by or as if by pressing
“compress the data”
a cloth pad or dressing (with or without medication) applied firmly to some part of the body (to relieve discomfort or reduce fever)
Synonyms, antonyms and the broader and narrower relations for compress come from Princeton University’s WordNet. Full sources and licences.