Definition
Latin abbreviation for quod erat demonstrandum: "Which was to be demonstrated." Q.E.D. may appear at the conclusion of a text to signify that the author's overall argument has just been proven.
Illustrative caselaw
See, e.g. Stupak-Thrall v. U.S., 89 F.3d 1269, 1299 (6th Cir. 1996).