A high-quality, extremely expensive wine produced in very small quantities.
Garage wines are the in-thing in Bordeaux. In the past, big estates were characterised by the brands they made on their large tracts of land. Largely the brainchild of Rolland, garage wines adopt a Burgundian approach: you select a minute piece of soil and throw a small fortune at it. You pare down the yields to nothing but a few healthy grapes and vinify them in spanking new oak barrels, then charge a king's ransom for a few oversubscribed bottles.
Giles MacDonogh, "Depardieu with a nose for glamour," The Financial Times (London), May 4, 2002
Felicia Rogan, owner of Oakencroft Vineyards, became interested in viticulture after she and her husband pressed a large quantity of grapes into what she termed "garage wine." She now guides the destiny of a 17-acre plot in Albermarle County.
Ralph W. Sheehy, "Is Virginia for Wine Lovers?," Washington Business Journal, August 11, 1986
Here's the earliest citation for the defined sense of the phrase:
Of the "garage wines", the tiny production Pomerols and St-Emilions, Le Pin has been followed by Ch Valandraud, while this year's star is La Mondotte, a new St Emilion bottling which is being rationed at £2,000 a case.
Jancis Robinson, "1996s trickle out," Financial Times (London), May 24, 1997
The original garage wine is called Le Pin, and its grapes grow on a tiny, five acre plot in Pomerol, which is near St. Emilion in Bordeaux, France. The first vintage, from 1981, was so astonishingly good that other winemakers soon followed suit to create their own boutique wines (as small wine batches were originally called). Since most of these operations were housed in relatively modest accomodations the Le Pin wine cellar is in the basement of a beat up old farmhouse the French writer Nicholas Baby came up with the name vins de garage and called the vintners garagistes (gah.ruh.ZHEESTS; 1999).
A garage wine is also sometimes called a "Chateau garage" wine (2000), and other names for small-batch, high-quality wines are micro-wine (1998), micro-cuvee (MY.kroh-koo.vay; 2000), and cult wine (1985).
Note, too, that this term once referred to a wine made at home, usually in a person's basement or garage, but that sense has fallen into disuse since the earliest citation in 1986.