The term 'Cocktail Vessel' can be defined as a GLASS with five letters. This type of vessel is commonly used to serve cocktails, such as martinis, margaritas, and other mixed drinks. It is usually made of GLASS and has a stem or handle for easy handling. The shape of the GLASS can vary, but it is typically tall and slender. Cocktail vessels are often decorated with intricate designs or patterns to add to the presentation of the drink.