A friend sent me a link to a Wikipedia article on Foehns. In it was a(nother) word I'd never heard of: adiabatic.

Acc'g. to AHD, it is: ADJECTIVE:

Of, relating to, or being a reversible thermodynamic process that occurs without gain or loss of heat and without a change in entropy.

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ETYMOLOGY:
From Greek adiabatos, impassable : a-, not ; see a- 1 + diabatos, passable ( dia-, dia- + batos, passable from bainein, to go; see gw- in Indo-European roots)

The wiki article (or rather, a link in it) says: Adiabatic heating or cooling of a gas results from pressure change. Work is done on or by the gas, but there is no heat transfer with the environment. Heat can be supplied to the gas by friction however. If an adiabatic process is frictionless too, the process is reversible and can be called isentropic.

Apparently it is pronounced addy-uh-BATtic.