1a surface or shape exposed by making a straight cut through something, especially at right angles to an axis:the cross section of an octahedron is a squarein cross section the sailfish’s body looks like a tapering spear
a thin strip of tissue or other material removed by making two straight parallel cuts through it.
2a typical or representative sample of a larger group:a cross section of our senior managers
3 Physics a quantity having the dimensions of an area which expresses the probability of a given interaction between particles.
(cross-section) [with object] make a cross section of: (as noun cross-sectioning)complex triangular terrain models for contour cross-sectioning
cross section in other Oxford dictionaries
Definition of cross section in the US English dictionary