Adiabatic process is a process in which there is no heat exchange between the surrounding and the gas.
So for example if an expansion happens really fast this process is adiabatic because there is no time for the heat to get transfered.
My professor said that we can describe this situation with ideal gas laws. But how can you do that while ideal gas law only hold in equilibrium states and if the process happens very fast there is no enough time for the pressure to become equilibrium pressure?
What we can calculate is if we make a box that is completely isolated and lower the pressure slowly.