1. Tubing, the outside diameter and wall thickness of which are identified by one of the pipe specification systems, such as IPS or EMT; otherwise, pipe is indistinguishable from other tubular materials. Because pipe specification systems use a nominal value to specify the outside diameter instead of the actual value — e.g., the outside diameter of 1 1/2″ IPS pipe is 1.900″ — one should be alert to this fact when tubing is referred to as “pipe” to ensure the diameter is correctly identified.
2. Jargon for tube in the automobile industry, especially when referring to exhaust systems. In this case, the outside diameter and wall thickness specifications of automotive “pipe” are actual, not nominal, values.