Logician's triumphant sign-off

• Geometric postscript
• Gertrude Stein's first novel, published posthumously as "Things As They Are"
• A relativistic quantum theory of the electromagnetic interactions of photons and electrons and muons
• Last letters of a math proof
• Logician's abbr.
• Logician's signoff
• Proof's end
• Proof closer
• Latin abbr. used in math proofs

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. ...