WordNet records no synonym and no antonym for mirror. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
polished surface that forms images by reflecting light
Synonyms, antonyms and the broader and narrower relations for mirror come from Princeton University’s WordNet. Full sources and licences.
a faithful depiction or reflection
“the best mirror is an old friend”
reflect as if in a mirror
“The smallest pond at night mirrors the firmament above”
reflect or resemble
“The plane crash in Milan mirrored the attack in the World Trade Center”