bracket has 4 distinct synonyms spread across 4 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. 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.
a category falling within certain defined limits
either of two punctuation marks (`<' or `>') used in computer programming and sometimes used to enclose textual material
either of two punctuation marks ([ or ]) used to enclose textual material
support with brackets
“bracket bookshelves”
Synonyms, antonyms and the broader and narrower relations for bracket come from Princeton University’s WordNet. Full sources and licences.