What does a cork mean?

A cork is seal for a bottle. Traditionally, corks were made out of a type of aged wood. Nowadays, most corks are made out of plastic, though wooden corks are still used for higher end wines. The verb form of cork means to close or sealsomething. The idiom, put a cork in it, means to stop speaking.
Cork is the buoyant, light brown substance obtained from the outer bark layer of the cork oak. It is used to seal bottles.