Reductor Curse

"With this powerful curse, skilled wizards can easily reduce obstacles to pieces. For obvious reasons great care must be exercised when learning and practising this spell, lest you find yourself sweeping up in detention for it is all too easy to bring your classroom ceiling crashing down, or to reduce your teacher's desk to a fine mist."

- Miranda Goshawk

The Reductor Curse (Reducto ) is a curse that can be used to blast solid objects into pieces. It is rather easy to reduce a target to a fine mist or a pile of ashes.

Harry Potter taught this curse to Dumbledore's Army during the 1995-1996 school year.

Known uses and practitioners
"Five different voices behind him bellowed, "REDUCTO!" Five curses flew in five different directions and the shelves opposite them exploded as they hit; the towering structure swayed as a hundred glass spheres burst apart, pearly-white figures unfurled into the air and floated there, their voices echoing from who knew what long-dead past amid the torrent of crashing glass and splintered wood now raining down upon the floor —"

- D.A. members smashing the selves in the Hall of Prophecy

Etymology
The incantation "reducto" is Latin for "reduce" or "bring down" 

Behind the scenes
In the film version of The Order of the Phoenix, only Ginny casts the Reductor Curse to smash the shelves in the Hall of Prophecy, instead of every D.A. member present.

Appearances

 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 1
 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)
 * LEGO Harry Potter: Years 1-4
 * LEGO Harry Potter: Years 5-7
 * Wonderbook: Book of Spells

Notes and references
Sortilège de Réduction Редукто Poistujo Reducto