rich has 12 distinct synonyms spread across 5 of its 13 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 poor, lean.
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.
possessing material wealth
“her father is extremely rich”
having an abundant supply of desirable qualities or substances (especially natural resources)
“blessed with a land rich in minerals”
high in mineral content; having a high proportion of fuel to air
“a rich vein of copper”
suggestive of or characterized by great expense
“a rich display”
people who have possessions and wealth (considered as a group)
“only the very rich benefit from this legislation”
4 of the 13 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for rich.
Synonyms, antonyms and the broader and narrower relations for rich come from Princeton University’s WordNet. Full sources and licences.