Cross section (geometry)

intersection of a body in 3D space with a plane

A cross section is what one gets if one cuts an object into slices.

A 2-D cross-sectional view of a compression seal.
A 3-D view of a beverage-can stove with a cross section in yellow.

In geometry the correct definition of cross section is: the intersection of a body in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane.

A cross section, or section is also an orthographic projection of a 3-dimensional object from the position of a plane through the object. A floor plan is a section viewed from the top.