from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Of or relating to hot water.
- adj. Geology Of or relating to hot magmatic emanations rich in water.
- adj. Geology Of or relating to the rocks, ore deposits, and springs produced by such emanations.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. of, or relating to hot water
- adj. of or relating to emanations of hot water that are rich in minerals, or to the rocks formed from them
from the GNU version of the Collaborative International Dictionary of English
- adj. Of or pertaining to hot water; -- used esp. with reference to the action of heated waters in dissolving, redepositing, and otherwise producing mineral changes within the crust of the globe.
- adj. of, pertaining to, or using the hot waters or steam found at special locations within the earth's crust.
from The Century Dictionary and Cyclopedia
- Of or relating to heated water: specifically applied to the action of heated waters in producing geological changes by dissolving mineral substances and redepositing them when cooled.
hydro- + thermal (Wiktionary)