Other forms: skiing; skis; skied
Skis are sporting equipment—long, thin pieces of wood, plastic, or metal that you strap to your feet so you can glide across the snow or down a snowy hill.
To slide down a mountain on skis is to ski. You can also cross country ski, or move across flat, snowy ground and gentle hills on skis. The special boots that skiers wear are called ski boots, and you also need a ski helmet and ski goggles when you go skiing. In its earliest English use, the word was spelled skee, and it's rooted in the Old Norse skið, "long snowshoe."