A private lunch is a meal that is eaten in a private setting, usually away from the public. It is often used to describe a meal that is shared between two or more people in a private setting, such as a home or office. The term 'MESS' is a four-letter word that is used to describe a situation that is chaotic, disorganized, or confused. In this context, it could be used to describe a private lunch that is unplanned and chaotic.