What is the general term used to refer to a break in the metallic continuity of the part being tested?

The general term used to describe a break in the metallic continuity of the part being tested is "discontinuity." In materials testing, discontinuities can encompass a broad range of flaws, including cracks, voids, inclusions, or other imperfections that disrupt the uniformity of the material. It is important to recognize that the term is not limited to a specific type of flaw; rather, it serves as an overarching category that includes various irregularities in the material that could potentially affect its integrity and performance.

Understanding this concept is crucial in visual testing and other inspection methods, as identifying any discontinuities can help assess the quality and reliability of the material or component. The other terms listed, such as "crack," "seam," and "lap," refer to specific types of discontinuities or features but do not capture the full range of potential irregularities as the term "discontinuity" does. Thus, it is appropriate to use "discontinuity" when describing any break in metallic continuity during testing.