adiabat
noun
adi·a·bat
ˈa-dē-ə-ˌbat
variants or less commonly adiabatic
ˌa-dē-ə-ˈba-tik 
ˌā-ˌdī-ə-
plural -s
: a curve or line plotted using coordinates selected to represent the pressure and volume or the temperature and entropy of matter during an adiabatic process
Word History
Etymology
adiabat, back-formation from adiabatic, adjective; adiabatic, from adiabatic, adjective
First Known Use
1872, in the meaning defined above