1. a section made by a plane cutting anything transversely, esp. at right angles to the longest axis.
2. a piece so cut off.
3. a photograph, diagram, or other pictorial representation of such a section.
4. the act of cutting anything across.
5. a typical selection; a sample showing all characteristic parts, relationships, etc.: a cross section of American opinion. 6. Survey.a vertical section of the ground surface taken at right angles to a survey line.
7. Also called nuclear cross section.Physics.a quantity expressing the effective area that a given nucleus presents as a target to a bombarding particle, giving a measure of the probability that the particle will induce a reaction.
Pronunciation: (krôs'sek'shun, kros'-),[key] —adj. Also,cross'-sec'tion•al.of or pertaining to a cross section.