retrograde has 7 distinct synonyms spread across 5 of its 9 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 2 recorded opposites are direct, anterograde.
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 backward in an orbit, of celestial bodies
move in a direction contrary to the usual one
“retrograding planets”
get worse or fall back to a previous condition
moving from east to west on the celestial sphere; or--for planets--around the sun in a direction opposite to that of the Earth
of amnesia; affecting time immediately preceding trauma
going from better to worse
moving or directed or tending in a backward direction or contrary to a previous direction
Synonyms, antonyms and the broader and narrower relations for retrograde come from Princeton University’s WordNet. Full sources and licences.