To call upon someone to be present, especially as a defendant or witness in a law court. The judge summoned the witness to testify in the trial.
To urgently demand or call for someone to come. The manager summoned the team to the conference room for an emergency meeting.
To muster or bring forth (a feeling, quality, or resource) from within oneself. He summoned all his courage to address the crowd.
To call forth a spirit or supernatural being by magical means. The sorcerer attempted to summon a powerful spirit to aid him in his quest.