installation has 6 distinct synonyms spread across 3 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.
the act of installing something (as equipment)
“the telephone installation took only a few minutes”
a building or place that provides a particular service or is used for a particular industry
“the assembly plant is an enormous facility”
a formal entry into an organization or position or office
“his initiation into the club”
Synonyms, antonyms and the broader and narrower relations for installation come from Princeton University’s WordNet. Full sources and licences.