What does adiabatic mean?
The definition of adiabatic
Ad`i*a*bat”ic, a.
Etym: [Gr. (Physics)

Not giving out or receiving heat.

— Ad`i*a*bat`ic*al*ly, adv. Adiabatic line or curve, a curve exhibiting the variations of pressure and volume of a fluid when it expands without either receiving or giving out heat. Rankine.