Cap : The thick layer of skins, stems and seeds that forms at the surface of fermenting red wine. Cap management, or breaking up the cap to increase contact between the skins and the liquid, is important since red wines extract color and flavor from the skins.
Capsule: The metal or plastic protective coating that surrounds the top of the cork and the bottle. Before pulling out the cork, at least the top portion should be removed to expose the cork and the lip of the bottle.
Mercaptans: Also known chemically as thiols, mercaptans are organosulfur compounds that emit unpleasant, skunky aromas of rubber, sulfur or garlic. Mercaptans are often encountered in wines suffering from reduction (in which case exposure to oxygen may alleviate the flaw) as well as in very old white wines.
Screwcap: A metal twist-off closure for wine bottles; an alternative to cork.
Reduced: Commonly used to describe a wine that has not been exposed to air and has developed stinky aromas due to reductive chemical reactions (as opposed to oxidation). Reduced notes in a wine generally result from the presence of volatile sulfur compounds, or mercaptans; these notes include rotten eggs, rubber, struck matches, sewage and even skunk. These off aromas may dissipate after exposure to air through decanting or swirling the wine in the glass.
Composite cork: Also known as an agglomerated cork. A wine bottle stopper made of particles or granules of natural cork pressed together and bound by an FDA–approved glue.