A spell in the Harry Potter series that cuts the target several times
like a sword. It was invented by Severus Snape and chronicled in his annotated Potions schoolbook, where Harry Potter learned it. The cuts can only be healed immediately after infliction by a countercurse also created by Severus Snape.
The spell is ineffective on Inferi or other creatures who do not have or need
blood.
The name derives from the Latin sectum, "
cut", and semper, "always"