"It's not easy, Apparition, and when it's not done property it can lead to nasty complications. This pair I'm talking about went and splinched themselves. ...They left half of themselves behind. ...So, of course, they were stuck. Couldn't move either way. Had to wait for the Accidental Magic Reversal Squad to sort them out. Meant a fair old bit of paperwork, I can tell you, what with the Muggles who spotted the body parts they'd left behind....."
-- Arthur Weasley (GF6)
When apparition goes wrong, a body part (or two) might be left behind.
References from the canon
- Splinching is obviously painful and dangerous, therefore some wizards choose other methods of transportation (GF6). Harry admitted to both Dumbledore and Ron that he preferred traveling by broom (HBP4, HBP18).
- Those who try to apparate illegally and splinch are sorted out by the Accidental Magic Reversal Squad (GF6).
- Apparition Instructor Wilkie Twycross refers to splinching as "the separation of random body parts" (HBP18)
- When Susan Bones splinched during lessons, the Heads of Houses put her back together with "a great bang and a puff of purple smoke" (HBP18).
- Ron lost half his eyebrow when taking one of his Apparition tests (HBP22). Later when he, Harry and Hermione had to hurriedly disapparate from Grimmauld Place to escape the Death Eaters, Ron splinched, scooping off part of his arm causing loss of blood. Hermione treated the wound with Essence of Dittany (DH14).
- Apparating across great distances to other countries is illegal due to fears of "extreme splinching" according to WOMBAT Test 3 (JKR-W3).
Seems to be a combination of "split" and "pinch" as if a body part is caught in a door.