"And Vaisey off too, he’s their best goal-scorer...."
-- Ron Weasley (HBP14)
Vaisey is a Chaser on the Slytherin Quidditch team in 1996 and is considered to be their best goal-scorer that season. A Bludger hit him in the head during a practice session, so he was unable to play in their match against Gryffindor (HBP14).
High goal-scoring Quidditch Chaser
Vaisey derives from the Anglo-Norman-French word enveisie ("playful, merry") and comes from Old French envoisie ("to sport, enjoy oneself") (Internet Surname Database).
Vaisey is no more than a year older than Harry, since he was on the team in Harry's sixth year. As he hadn't appeared before, he could therefore be younger than Harry.
Lexicon list of Chasers
From the Web
Harry Potter Wiki: Vaisey