igneous

American Heritage® Dictionary of the English Language, Fourth Edition

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

Century Dictionary and Cyclopedia

1. Pertaining to, consisting of, having the nature of, or resembling fire: as. igneous particles; igneous appearances.
2. Produced through the agency of fire, or as the result of volcanic and eruptive forces: used in geology in contradistinction to aqueous. A rock has an igneous origin when it has been discharged from a volcano; it has an aqueous origin when deposited from water. All aqueous rocks are made up of the debris of igneous ones, with the exception of such as are the result of organic agencies —that is, such as have been formed through the agency of plants or animals. Some rocks, however, are at the same time of both aqueous and igneous origin, as when volcanic ashes are thrown into water, and deposited in a stratified form.

Wiktionary

1. adj. Pertaining to, having the nature of fire; containing fire; resembling fire; as, an igneous appearance
2. adj. Resulting from, or produced by, the action of great heat; with rocks, it could also mean formed from lava/magma; as, granite and basalt are igneous rocks

GNU Webster's 1913

1. adj. Pertaining to, having the nature of, fire; containing fire; resembling fire.
2. adj. Resulting from, or produced by, the action of fire.

WordNet 3.0

1. adj. like or suggestive of fire
2. adj. produced by the action of fire or intense heat
3. adj. produced under conditions involving intense heat