igneous has 4 distinct synonyms spread across 3 of its 3 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 aqueous.
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.
produced under conditions involving intense heat
“igneous rock is rock formed by solidification from a molten state; especially from molten magma”
like or suggestive of fire
“a fiery desert wind”
Synonyms, antonyms and the broader and narrower relations for igneous come from Princeton University’s WordNet. Full sources and licences.