1. a very large rock, typically one that has been worn smooth by water or weather

Examples

• The hikers climbed over a massive boulder blocking the trail.
• Ancient glaciers left huge boulders scattered across the valley.
• She sat on a smooth boulder by the stream to rest.
• The landslide sent boulders tumbling down the mountainside.
• Children love to climb on the large boulder in the park.
• The river carved its way around the enormous boulder.