involved has 6 distinct synonyms spread across 2 of its 5 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 uninvolved.
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.
connected by participation or association or use
“we accomplished nothing, simply because of the large number of people involved”
entangled or hindered as if e.g. in mire
“the difficulties in which the question is involved”
highly complex or intricate and occasionally devious
“the Byzantine tax structure”
2 of the 5 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for involved.
Synonyms, antonyms and the broader and narrower relations for involved come from Princeton University’s WordNet. Full sources and licences.