Etym: "Madam" Helena Petrovna Blavatsky was one of the most famous spiritualists, and the founder of modern theosophy.
vampires: Essentially, semi-human creatures who drink blood; the details of the legend have gone through many variations over the centuries. Rowling's vampires retain the aversion to garlic, though the exact mechanism by which it wards them off is yet to be explained; they are also recognizable in part by being very pale and gaunt. Modern Dracula-inspired mythology insists on a kinship with bats and a predilection for wearing black. Okay, kids, now keep a sharp lookout!
Vanishing Spell: Might be something to render a person invisible or unnoticed, or another term for Apparation.
Vauxhall Road: A major thoroughfare in London. Tom Riddle bought a diary there.
Vector: Last name of the witch who teaches Arithmancy at Hogwarts.
Etym: From the mathematical term.
Venemous Tentacula: A spiky, dark red plant that has teeth.
Vernon Dursley: Etym: Alternative for vernal in 1658, or a surname derived from a common placename in France.
Veronica Smethley: Etym: Corrupted form of Latin vera icona, "true image". St. Veronica is a legendary figure who is said to have wiped perspiration from Jesus's face as he carried his cross; the cloth used retained an image. Also the name of a plant genus.
Vincent Crabbe: Etym: From a derivative of Latin vincens, "conquering". The name of a 3rd century martyr, and St. Vincent de Paul (1580-1660), remembered for his clinics and works of charity. A bit closer to the character we're talking about, also used in 1592 to mean the dupe in a betting game.
Vindictus Viridian: Etym: From the same root as vindictive and meaning pretty much the same thing.
Viridian, Vindictus (PS ch. 5): Author of Curses and Countercurses.
Etym: Strong green; technically, Veronese green. In this case, the green of jealousy or envy.
Voldemort: The Dark Lord; He Who Must Not Be Named. His rule was cut short by a curse that rebounded on him when he tried to kill the infant Harry and left him a shapeless wraith. Wand: 13 1/2", yew and phoenix feather.
Etym: Probably derived from French vol-de-mort, "flight of death". Beastly equation for "L*rd V*ld*m*rt": a=30, b=33, etc.
Voyages with Vampires: One of Gilderoy Lockhart's books.