Original jurisdiction is the special power given to the Supreme court of United States where a case of certain matter can be directly brought up in the Supreme court.
In other words, original jurisdiction is the power of the court to hear a case for the first time in the court unlike for the appellate jurisdiction which only has the power to review the jurisdiction of any subordinate court.
In the context, a case file by California on the river pollution against Nevada which can be directly brought in the Supreme court is an example of the Original jurisdiction of the Supreme court.
