Any movies, shows, stories, comics, art, and any other printable, or recordable material, commonly of the horror genre, that tailors to extreme violence, gore, and mutilation.
"She's been on a Nightmare on Elm St. marathon lately, though I couldn't watch that much gorenography without developing some disturbing problems."
Movies: Hostel, Friday the 13th
Books: It by Steven King, Terry Goodkind's Sword of Truth series is quite explicit also
Music: Gwar, Cradle of Filth
Comics: Vault of Horror, some stories in Heavy Metal tend to be blood and guts and not much else