Denoting equal pressure; as, an isobaric line; specifically, of or pertaining to isobars.

Having constant pressure.

this is a way to conduct a process. Other ways are isothermal or adiabatic and so on. A process is said to be isobaric, if the pressure is held constant during the process

Literally: same pressure. An isobaric energy recovery device, like the PX, includes chambers wherein the pressure of two volumes of water equalizes.

At constant pressure.

Of equal or constant pressure, with respect to either space or time.