In general terms, we can assume that an amplifier has a certain forward and backward transmission, in so far the load of one port affects the impedance of the other. The effect may be negligible for some amplifiers, e.g. low and medium frequency OPs.
There are different ways to specify a linear two-port.
https://en.wikipedia.org/wiki/Two-port_network
If you refer to impedance parameters (Z-parameters), the other port would be connected open circuit, not shorted, according to the nature of the parameter set.