Big waves are a phenomenon that can occur in the ocean, often caused by strong winds or seismic activity. The term 'big waves' can refer to several different types of waves, including swells, tsunamis, BILLOWS, and combers. Swells are large, long-period waves that form when wind blows over a large area of open water. Tsunamis are huge waves that are caused by underwater earthquakes or volcanic eruptions. BILLOWS are large, rolling waves that form when wind blows over a large area of open water. Combers are large, powerful waves that form when wind blows over a shallow area of water.