What is dry champagne?

Dry Champagne refers to the amount of sugar content, or sweetness, of the Champagne. The dry description can be misleading for sparkling wine. A still wine described as dry means the wine is not sweet. However, the opposite is true for Champagne which is labeled Dry for sweeter and Brut for less sweet.

Source: http://en.wikipedia.org/wiki/Champagne_%28wine%29

Source: The Widow Clicquot: The Story of a Champagne Empire and the Woman Who Ruled It