Tubing is the activity of floating down a river or sliding down a snowy hill while sitting in a large inflated inner tube. On a hot summer day, you might go river tubing, letting the current carry you gently downstream while you relax and splash with friends. In winter, a ski resort might have a tubing hill where you zoom down snowy slopes, spinning and bouncing as you go.

The tubes used for tubing are like giant rubber donuts, originally designed to go inside truck or tractor tires. They're tough enough to bump over rocks in a stream or slide across snow and ice. Snow tubing parks often have special lanes and lifts to carry you back to the top, while river tubing might be a lazy afternoon drifting between swimming holes.

The word can also refer to tubes as a material. Scientists use rubber tubing in laboratories to move liquids between containers. Hospitals use plastic tubing for IVs. In these cases, tubing means flexible hollow cylinders that carry water, air, or other substances from one place to another.