v.1. To increase something, especially in stages: The factory stepped up production to meet the growing demand. The runners stepped their pace up for the last two laps.
2. To come forward: When I call your name, please step up and be counted. The speaker stepped up to the podium and addressed the crowd.
3. To improve one's performance or take on more responsibility, especially at a crucial time: You need to step up and take responsibility for your actions. The player stepped up at a crucial moment and scored the winning point.