A runtime variable that you wish to reset to its default value. See SET" for more information on available variables.
Use the RESET command to return runtime variables to their original values. For more information about values allowed for these variables, and what the original values were, refer to SET."
You can also issue the following command to accomplish the same effect:
SET variable TO DEFAULT
The following example resets a variable called SEED to its default value:
testdb=# RESET SEED; RESET VARIABLE