German wine glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Oak
A type of hardwood commonly used for building wine barrels. American oak has a distinctive, bourbon-like flavour while the French oak flavour is more subtle. Both types of oak barrels contribute considerable tannin and vanillin (vanilla) flavours to wines during aging.
Oak Root Fungus
See Armillaria.
Oaky
Tasting term to describe the smell or taste of excessive oak flavour in a wine.
Oechsle
(pronounced "ex'-a-luh") German density scale used to estimate the ripeness of grapes and predict the eventual alcohol content of a wine produced from those grapes.( based on specific gravity)
Oenology
Original Greek spelling of Enology, (now usually anglicized to Enology).
Offene Weine
Open wine or caraffe wine served in pubs and restaurants.
Oidium 
French word for the fungal vine disease "powdery mildew."
Open-top tanks
Wine tanks which have no permanent covers, used only for red wine fermentation. This is the traditional design for fermenters, but modern wineries now use only the closed-top design. Open top tanks are more difficult to keep clean, allow loss of volatile wine flavour during warm fermentations and require some type of surrounding building or roof in case of rain. Oh, yes, and they call for some method to keep birds from roosting directly overhead.
Optima for a full list of grapes click HERE
(white grape) crossing of Riesling and Sylvaner grape with the Muller-Thurgau. Widely grown in the Rheinhessen and the Mosel-Saar-Ruwer region of Germany and used for blending purposes in the white wines of the region. It can easily reach high sugar levels, there are about 200 ha planted
Originalabzug
Term sometimes found on German wine labels to denote "Estate Bottled."
Ortega for a full list of grapes click HERE
white Grape cross between Muller-Thurgau and Siegerrebe varieties. Developed in W ü rzbrg in 1948. Used for white wine blending in the Rheinhessen region of Germany. Produces flavourful wines that have earned the Prädikat rating in good vintages. Ripens early-mid September. Cold-hardy and has good resemblance to the Riesling grape with which it is often blended in order to enhance flavour in poor vintages.1000 ha planted in Rheinhessen the Mosel and Franken regions.
Ortsweine
High-quality wines that reflect regional character.At least 80% of an estate’s holdings must be planted with traditional grape varieties Typical of their region, as recommended by the VDP. Maximum yield 75hl/ha. Minimum must weight (higher than prescribed by law) Is determined by the regional associations.
Osmosis
The natural movement of fluids through a membrane or porous partition such as a cell wall. Fluid always tends to move through the membrane towards a solution of higher concentration, in an effort to equalize the concentrations on both sides of the membrane.
Oraniensteiner for a full list of grapes click HERE
This white grape is a white-wine producing variety released by the Geisenheim Research Institute in 1985 and is the result of a Riesling x Silvaner (Gruen) crossing. Has the synonym names Geisenheim 11-34 and Hochkroner).
Ouillage
Act of topping wine barrels in an effort to keep the barrels refilled as they lose volume due to evaporation of liquid through the barrel staves. Topping barrels is traditional but recent work shows that to top barrels during aging actually adds oxygen to the wine rather than protecting it from oxygen!
Overcropped
A vine which carries more crop than it can reasonably ripen. Vines which aren't pruned drastically enough tend to set too much crop. Wine produced from fruit of an overcropped vine is always poorer in quality than if the crop were of normal size.
Overcropping
The act of allowing vines to set too much fruit (usually by pruning too lightly in winter).
Oxidation
Adverse change in wine flavour, stability and/or colour caused by excessive exposure to air.
Oxidized
Flavour term to describe a wine which has suffered excessive oxidation. During oxidation, wines lose their original fruitiness and take on a darker colour, eventually becoming quite brown. The fruity flavour is replaced by one reminiscent of "vegetable soup," later becoming nutty or maple-like and, finally, meat-like and dead.
Wine villages beginning with 
click the village name for a list of its einzellagen (individual vineyards)
