Proof initials

• Euclidean abbr.
• End of many an argument
• Geometer's sign-off
• Mathematician's sign-off
• Relative of "voilà!"
• It's often caught by proof readers
• Relative of "VoilГ !"

Wiktionary Word definitions in Wiktionary
alt. quod erat demonstrandum (Latin ''what had to be proved'' or ''what was to be demonstrated''). interj. quod erat demonstrandum (Latin ''what had to be proved'' or ''what was to be demonstrated''). n. quantum electrodynamics.

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
QED \Q.E.D\, QED \QED\(k[=u]"[=e]*d[=e]"), interj. [From Latin, quod erat demonstrandum, i.e. which was demonstrated.] Which was demonstrated; -- a phrase used after the conclusion of some line of reasoning, especially in mathematical or logical proofs. ...