What do you think what is output impedance?
Our electronic definitions web site has answer for that as well:
another term used for the Thevenin impedance of an amplifier. It means the amplifier has been Thevenized, so that the load sees only a single resistance in cries with a Thevenin generator. 7ltis single resistance is the Thevenin or output impedance.
Other electronic terms somewhat related to output impedance
closed loop quantity