Boozy Biddies definition: sugar syrup
This is the wine and sugar mixture that is added to a bottle of sparkling wine at the end of the production process. It effects how sweet the wine is and can lend some other flavor characteristics to the bottle.
From the San Francisco Chronicle:
Pronounced like it’s French (doe-SAHJ), dosage, sometimes called a liqueur d’expedition, refers to the wine-and-sugar mixture that’s added to a bottle of sparkling wine at the very end of the production process. It happens after disgorgement — when the lees, or dead yeast cells, that have collected in the neck of the bottle are expelled. (No one wants a bunch of dead yeast cells in their bubbly.) But what, precisely, the dosage consists of determines the taste of the wine. Small amounts of sugar may still result in a dry-tasting wine if the sugar is balancing high, tart acidity. Wines labeled “demi-sec” or “doux” will have quite a bit of sugar and will taste sweet. “Brut” and “Extra Brut” wines taste dry. Wines labeled as Brut Nature or Brut Zero, which have no dosage added, will taste drier still, and possibly a little too austere for some palates.