The Collaborative International Dictionary
Isopiestic
Isopiestic \I`so*pi*es"tic\, a. [Iso- + Gr. ? to press.] (Thermodynamics) Having equal pressure.
Isopiestic lines, lines showing, in a diagram, the relations of temperature and volume, when the elastic force is constant; -- called also isobars.
Wiktionary
isopiestic
a. isobaric