What is "latus rectum"

Latus rectum \La"tus rec"tum\n. [L., the right side.] (Conic Sections) The line drawn through a focus of a conic section parallel to the directrix and terminated both ways by the curve. It is the parameter of the principal axis. See Focus, and Parameter.

n. (context geometry English) The line drawn through a focus of a conic section parallel to the directrix and terminated both ways by the curve. It is the parameter of the principal axis.