Sectum Sempra

Sectum Sempra is a spell used in Harry Potter and the Half-Blood Prince. The spell causes the victim to bleed uncontrollably. Harry uses it on Draco Malfoy in Chapter 21 of the sixth book. Harry learns it in a book that he believes is Lord Voldemort's but is actually Professor Snape's.

In latin, Sectum Sempra translates to may mean cut forever.