%cross section%

n. 1. a flat plane cutting through a three-dimensional object, usually at right angles to the longest axis of the object. [ PJC ]

2. any visual representation of a cross section{ 1 }, showing the internal structure of the object in the plane of the cross section; as, the technician prepared a series of MRI cross sections of the skull. Different cross sections created by different techniques may show different aspects of internal structure. Thus computerized axial tomography using X-rays shows different structures than are visualized by MRI. [ PJC ]

3. a thin slice of an object made by cutting it transversely; as, to view a cross section of a bacterium with an electron microscope after staining the DNA; cross sections were prepared with a microtome. [ PJC ]

4. a representative sample of a complex group; as, the town contained a cross section of the American population. [ PJC ]

5. (Physics) a measure of the probability that a nucleus will interact in a specified way with a bombarding particle, expressed as the effective area that the nucleus presents to the particle; -- called also nuclear cross section. [ PJC ]