poor has 12 distinct synonyms spread across 3 of its 6 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 one recorded opposite is rich.
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.
having little money or few possessions
“deplored the gap between rich and poor countries”
characterized by or indicating poverty
“the country had a poor economy”
lacking in quality or substances
“a poor land”
people without possessions or wealth (considered as a group)
“the urban poor need assistance”
Synonyms, antonyms and the broader and narrower relations for poor come from Princeton University’s WordNet. Full sources and licences.