1. 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 - pyrogenic strata • Syn: igneous, pyrogenic • Pertains to noun: heat, heat (for: pyrogenic), heat (for: igneous) 2. produced by or producing fever • Syn: pyrogenic, pyrogenetic • Pertains to noun: pyrogen (for: pyrogenetic), pyrogen, pyrogen (for: pyrogenic) • Derivationally related forms: pyrogen