The summit is the highest point of a mountain. When climbers reach the summit of Mount Everest, they stand at the top of the world, 29,032 feet above sea level. The summit is where the climbing stops because there's nowhere higher to go.

As a noun, summit means a meeting between important leaders, especially heads of government. When the President of the United States meets with other world leaders to discuss economic policy or peace treaties, that's called a summit. These meetings are called summits because the people attending are at the “top” of their governments, just like a mountain summit is at the top of the mountain.

You might hear someone say they're working to summit a difficult peak, using it as a verb. Or a scientist might say they're trying to surmount the challenges of a complex problem. In these cases, reaching the summit means achieving something that required serious effort and determination.