reflexion has 10 distinct synonyms spread across 7 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.
the phenomenon of a propagating wave (light or sound) being thrown back from a surface
expression without words
“tears are an expression of grief”
a remark expressing careful consideration
a calm, lengthy, intent consideration
the ability to reflect beams or rays
the image of something as reflected by a mirror (or other reflective material)
“he studied his reflection in the mirror”
Synonyms, antonyms and the broader and narrower relations for reflexion come from Princeton University’s WordNet. Full sources and licences.