|Muggles' Guide to Harry Potter - Magic
|Gouges channels in material
|Harry Potter and the Deathly Hallows
Defodio, a gouging spell, is used to cut channels or grooves in solid material.
Extended Description edit
Hermione uses this spell to carve space into the tops of tunnels as the Trio escape from Gringotts on the back of a dragon. Harry and Ron follow her lead, cutting away parts of the passages that the dragon is trying to get through as it finds its way out of the cellars of Gringotts.
It is interesting that spells are so very specific; it is noted that there are several different cleaning spells, Evanesco for inside containers, Scourgify for surfaces, and Tergeo for dust. Here we see that there is a specific spell for gouging surfaces; while it is similar to the other destructive curses, like the Reductor curse and Deprimo, it is not the spell that Hermione uses in this instance.
A large part of ability in Charms, then, must be the ability to remember the specific spell that would provide the wanted effect, out of a list of possibly hundreds or thousands, along with the ability to associate the correct gestures and mental state with it.