Cross section definition of cross section by The Free ...
cross section also crosssec·tion (krôs′sĕk′shən, krŏs′) n. 1. a. A section formed by a plane cutting through an object, usually at right angles to an axis. b. A piece so cut or a graphic representation of such a piece. 2. Physics A quantity, measured in units of barns, used to express the probability of an encounter between particles over a ...