Because if it's irreversible, it's very likely that I don't know what the pressure inside the system is doing while this is happening.

因为对不可逆过程，系统内部的压强,没有明确的定义,气体不处于平衡态。

麻省理工公开课 - 热力学与动力学课程节选

We're pretty much done with our definitions STUDENT: Was adiabatic reversible?

各种定义,学生：绝热过程是可逆的吗？

麻省理工公开课 - 热力学与动力学课程节选