Gigantic waves are often referred to as tsunamis, which is an 8-letter word. Tsunamis are large ocean waves that are caused by earthquakes, landslides, volcanic eruptions, and other underwater disturbances. They can reach heights of up to 100 feet and travel at speeds of up to 500 miles per hour. Tsunamis can cause immense destruction when they reach land, flooding coastal areas and causing significant damage to buildings and infrastructure.