northwest has 7 distinct synonyms spread across 5 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 northwestern region of the United States
the direction corresponding to the northwestward compass point
the compass point midway between north and west; at 315 degrees
a location in the northwestern part of a country, region, or city
situated in or oriented toward the northwest
to, toward, or in the northwest
Synonyms, antonyms and the broader and narrower relations for northwest come from Princeton University’s WordNet. Full sources and licences.