Glisseo

Glisseo is a charm that makes rough or rigid surfaces to become temporarily smooth and slippery. Hermione Granger used it to turn a staircase into a slide during the Battle of Hogwarts so that she, Harry Potter and Ron Weasley could avoid attacking Death Eaters.

It may also be the spell that transforms the stairs of the girls dormitories at Hogwarts to prevent boys from entering as the Hogwarts founders felt girls were more trustworthy than boys.

Etymology
From French Glisser, meaning "to slip/slide".

Appearances

 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Deathly Hallows