What you say when you don't want someone around. Namely the Cedric Diggory(ies, s?) of the world. Found in Harry Potter and the goblet of fire.
and more importantly, in the internet cult favorite musical, A Very Potter musical.
Quirrel/Voldemort/Brian/Joe : KILL THE SPARE! AVADA KEDAVERA!
A phrase now used to advocate the removal of a fat, unatractive or generally undesireable girl from a group of otherwise good talent
Titan: Yeah man, Kill the Spare!