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