- a top that screws on the top of a wine bottle, as a substitute for the traditional plug of cork. This is a modern solution to sealing a wine bottle, about which there is a huge debate in the wine industry. The increase in consumption of wine has meant that more corks are required, but the cork oak supply is limited, so corks are not always of perfect quality. They can contain bacteria, or be unsuitable for storing the bottle for a long time on its side, when the cork could dry out and shrink, allowing oxygen into the bottle. A screwcap solves these problems, but is not considered aesthetically pleasing by traditionalists.