pre-drinking
n.— «Because of the high cost of drinks in bars, those who can legally drink participate in what is known as “pre-drinking,” where they down as much as they can before they go out.» —“Mel’s Hell” by Georgie Binks CBC News (Canada) Aug. 11, 2006. (source: Double-Tongued Dictionary)
Further reading
In 1916, a small-town newspaper in Pennsylvania printed a fanciful item about a local gathering with a guest list that included, among others, Miss Ella Vader, Mr. Ray Zor, and other punny names. This is part of a complete episode. Transcript of...
Pete in Minneapolis, Minnesota, wonders about the word canooper, which he’s heard used to refer to a type of alcoholic beverage. Also spelled kanuper or canuper, this word is rarely found outside Minnesota. Its origin is uncertain, although Red...
It is usually called “pregaming” by the hip kids:
http://abcnews.go.com/GMA/Health/story?id=1085909&page=1
Nice, thanks, I’ve made a cite.