Hydrothermal \Hy`dro*ther"mal\, a. [Hydro-, 1 + thermal.]
1. 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.
[1913 Webster]
2. of, pertaining to, or using the hot waters or steam found
at special locations within the earth's crust; as,
hydrothermal power generation.
[PJC]