Definitions for qed
Random House Webster's College Dictionary
which was to be shown or demonstrated (used esp. in mathematical proofs).
Origin of Q.E.D.:
1810–20; < L quod erat dēmōnstrandum
quantum electrodynamics, QED(noun)
a relativistic quantum theory of the electromagnetic interactions of photons and electrons and muons
Quod erat demonstrandum (Latin what had to be proved or what was to be demonstrated).