adiabatic

19th-century coinage (introduced by W. J. M. Rankine in the 1860s) based on Ancient Greek ἀδιάβατος (adiábatos, “impassable”), used of terrain (rivers, forests) by Xenophon, from ἀ- (a-, “not”) + διά (diá, “through”) + βατός (batós, “passable”), from βαίνω (baínō, “to go”).

• IPA^(key): /ˌeɪdaɪəˈbætɪk/, /ˌeɪdɪəˈbætɪk/, /ˌædɪəˈbætɪk/
• Rhymes: -ætɪk

adiabatic (not comparable)

1. (physics, thermodynamics, of a process) That occurs without gain or loss of heat (and thus with no change in entropy, in the quasistatic approximation).
   • 1871, J. C. Maxwell, Theory of Heat, p. 129:

     The line drawn on the indicator diagram in the latter case has been named by Professor Rankine an Adiabatic line, because it is defined by the condition that heat is not allowed to pass through (διαβαίνειν) the vessel which confines the substance.

   • 2006, Thomas Pynchon, Against the Day, Vintage 2007, p. 737:

     Talk of dynamic compression and adiabatic gradients didn't carry as much weight as the certainty of its conscious intent.

2. (physics, quantum mechanics, of a process) That involves the slow change of the Hamiltonian of a system from its initial value to a final value.
   • 1961, Albert Messiah, Quantum Mechanics‎, volume II, page 740:

     In this section we examine the limiting cases when T is very small (sudden change) and very large (adiabatic change).

• (thermodynamics): diabatic
• (quantum mechanics): nonadiabatic

• adiabatic on Wikipedia.Wikipedia