Tubing/ˈtuːbɪŋ/ Definition 1 of 3Pro Tip 1/3Various Materials Tubing can be made from different materials depending on its use. The lab used glass tubing for the experiment. Pro Tip 2/3Practical Uses Tubing is often part of practical objects like machines or medical equipment. The mechanic replaced the old tubing in the engine. Pro Tip 3/3Sizes Vary The diameter and length of tubing can greatly vary, from very small to large. He cut the plastic tubing to fit the water filter.