Raise or extend the end of your discharge pipe so there is water standing in it after the pump shuts off. The end of your pipe should be at least 2 diameters (about 4 inches in your case) higher than the first low point that you encounter as you go back along the pipe in the direction of the pump, and preferably higher than the highest point in the discharge pipe. And it should always higher than the inlet of the pump (usually not an issue). That will produce a trap that will prevent air from entering the pipe as it drains.
If it is not possible to raise the pipe, then put a trap in it using elbows, or adjust the pipe inside so the last run of pipe is up hill.
It will take a while for the air that is in the pipe to be entrained with the water and be removed from the pipe. After that, you will not hear gurgling.
It will also slightly decrease the flow capacity of your pump.