Etym: No etymology.
wands: An essential tool for a wizard, used in nearly all magic (a notable exception being potions). Wands have four distinguishing characteristics: length, flexibility, the material used in the core, and the wood used for the exterior.
Wand cores are taken from magical animals: phoenix feathers, unicorn hairs,and dragon heartstrings have been mentioned so far. The core determines the "identity" of the wand. The significance of the wood used and the flexibility of the wand are not clear, but it appears to affect the type of magic it is best suited for. This lexicographer hesitates to offer a hypothesis on the significance of wand length.
Warlocks' Convention: Some kind of rule-making body or event. One in 1709 outlawed dragon breeding.
Weasley, Arthur [Wesseley]: The head of the Weasley clan; Ron's father.
Etym: Variation of the Russian patronymic Veselov, from a nickname meaning "cheerful".
Weasley, Bill: The oldest of the Weasley children. He became Head Boy during his time at Hogwarts. He now does "something for Gringotts".
Etym: See above.
Weasley, Charlie: Second-oldest of the Weasley children, he became captain of the Gryffindor Quidditch team when he was a student. Now, he is studying dragons in Romania.
Etym: See above.
Weasley, Fred and George: Twins, who are the Beaters on the Gryffindor Quidditch team, and inveterate pranksters.
Etym: See above.
Weasley, Ginny: Ron's sister, the youngest of the Weasleys, who will start at Hogwarts the year after Harry.
Etym: See above.
Weasley, Molly: Ron's long-suffering mother.
Etym: See above.
Weasley, Percy: One of Ron's older brothers, he became a prefect in Harry's first year. Noted for being fussy, rule-oriented, and in many other ways being the Arnold Rimmer of his class.
Etym: See above.
Weasley, Ron: Harry's best friend, a Gryffindor in the same year; the perfect sidekick in that he has no existence worth noting outside Harry's presence.
Etym: See above.
werewolf: So far the werewolves here appear to be the standard Western model, infected by another werewolf and turning into an unthinking man-eater when a full moon is above the horizon.
Werewolf Code of Conduct: Enacted in 1637, the specifics have not been given.
willow: Any shrub or tree of the genus Salix, grown variously for ornament, shade, or timber. Willow bark is the source for salicin, the parent of a whole set of pain relievers.
Wingardium Leviosa: The incantation for a levitation charm.
Etym: From wing or something similar, and Latin levis, "light".
Wood, Oliver: A Gryffindor, 4 years ahead of Harry, who is the Keeper and captain of the Gryffindor Quidditch team.
Etym: What it sounds like.
wormwood: Artemisia Absinthium, used as a tonic and vermifuge. One of the ingredients of the Draught of Living Death.