up has 5 distinct synonyms spread across 5 of its 14 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 down.
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.
being or moving higher in position or greater in some value; being above a former position or level
“the anchor is up”
extending or moving toward a higher place
5 of the 14 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 up.
Synonyms, antonyms and the broader and narrower relations for up come from Princeton University’s WordNet. Full sources and licences.
“the up staircase”