A mountaintop is the highest point of a mountain, where the slopes finally stop climbing and there's nowhere left to go but down. Standing on a mountaintop means you've reached the peak, the summit, the very top of that particular climb.

Mountaintops can be bare rock swept clean by wind, snow-covered peaks that gleam in sunlight, or gentle rounded tops covered in grass. Some mountaintops are so high that climbers need oxygen tanks to breathe. Others are modest hills you could reach in an afternoon hike with your family.

The word also describes something figurative: a mountaintop experience means a moment of great achievement, clarity, or joy. When you finally solve a problem you've worked on for weeks, or when your team wins the championship after a long season, those are mountaintop moments. They're the high points of life, the times when you feel you've reached something special after real effort.