1.Definition: like or suggestive of fire

"An igneous desert atmosphere"

Related Adjective(s):fiery

2.Definition: produced by the action of fire or intense heat

"Rocks formed by igneous agents"

Related Adjective(s):eruptive

3.Definition: produced under conditions involving intense heat

"Igneous rock is rock formed by solidification from a molten state; especially from molten magma", "Igneous fusion is fusion by heat alone"

Related Adjective(s):pyrogenic, pyrogenous