cross-section (Adjective) — Representing a plane made by cutting across something at right angles to its length. ex. "cross-section views of the neck"
cross-section (Noun) — A section created by a plane cutting a solid perpendicular to its longest axis.
cross-section (Noun) — (statistics) a sample meant to be representative of a whole population.
cross-section (Noun) — (physics) the probability that a particular interaction (as capture or ionization) will take place between particles; measured in barns.