upstage has 2 distinct synonyms spread across 1 of its 7 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 downstage.
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.
move upstage, forcing the other actors to turn away from the audience
steal the show, draw attention to oneself away from someone else
“When the dog entered the stage, he upstaged the actress”
Synonyms, antonyms and the broader and narrower relations for upstage come from Princeton University’s WordNet. Full sources and licences.
of the back half of a stage
“she crossed to the upstage chair forcing the lead to turn his back to the audience”
at or toward the rear of the stage
“the dancers were directed to move upstage”