write up has 5 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. 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.
bring to public notice by writing, with praise or condemnation
“The New York Times wrote him up last week”
Synonyms, antonyms and the broader and narrower relations for write up come from Princeton University’s WordNet. Full sources and licences.
a short account of the news
“the report of his speech”