1. Of, relating to, or characteristic of fire.
2. Geology.
   1. Formed by solidification from a molten state. Used of rocks.
   2. Of or relating to rock so formed; pyrogenic.

[From Latin igneus, from ignis, fire.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.