contrivance has 11 distinct synonyms spread across 4 of its 6 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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.
the faculty of contriving; inventive skill
“his skillful contrivance of answers to every problem”
an artificial or unnatural or obviously contrived arrangement of details or parts etc.
“the plot contained too many improbable contrivances to be believable”
any improvised arrangement for temporary use
Synonyms, antonyms and the broader and narrower relations for contrivance come from Princeton University’s WordNet. Full sources and licences.