Short definition
A fee charged by a restaurant for opening and serving a bottle of wine that you bring from home.
Many restaurants allow you to bring your own bottle (BYOB) for a corkage fee. It makes sense when you have a special bottle that is not on the wine list — a birth-year vintage, a gift, something you have been saving. Etiquette tip: do not bring a wine that is already on the restaurant's list, and consider offering the sommelier a taste. Some places waive corkage if you also buy a bottle from their list.