Opposed to sweet or fruity wine. In sweet wine some of the sugar is not yet decomposed; in dry wine all the sugar has been converted into alcohol. The doctoring of wine to improve its quality is called dosage.
“Upon the nature and amount of the dosage,the character of the wine (whether it be dry or sweet, light or strong) very much depends.” —Vizetelly: Facts about Champagne, chap. v. p.59.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Dry Wine from Infoplease: