Over-running is a term that describes the act of surpassing or exceeding a certain limit, boundary, or quota. The antonyms of over-running are falling short, underperforming, under-achieving, and failing to meet expectations. Falling short implies the inability to meet the required target or standard. Underperforming pertains to inefficient execution or poor results. Under-achieving is the term used when someone does not reach their potential, either due to lack of effort or skill. Failing to meet expectations pertains to the overall disappointment in the outcome of a situation. These antonyms are essential in differentiating performance levels and identifying areas that need improvement.