1. An ancient expression of good wishes on a festive occasion, especially in drinking to some one. Geoffrey of Monmouth relates, on the authority of Walter Calenius, that this lady Rowena, the daughter of Hengist, knelt down on the approach of the king, and, presenting him with a cup of wine, exclaimed, lord king waes heil, that is, literally, health be to you. (N. Drake)
2. An occasion on which such good wishes are expressed in drinking; a drinking bout; a carouse. In merry wassail he . . . Peals his loud song. The king doth wake to-night and takes his rouse, keeps wassail. (Shak) The victors abandoned themselves to feasting and wassail. (Prescott)
3. The liquor used for a wassail; especially, a beverage formerly much used in England at christmas and other festivals, made of ale (or wine) flavored with spices, sugar, toast, roasted apples, etc.; called also lamb’s wool. A jolly wassail bowl, A wassail of good ale. (old Song)
4. A festive or drinking song or glee. Have you done your wassail! ‘T is a handsome, drowsy ditty, I’ll assure you. (Beau. & Fl)
Origin: AS. Wes hal (or an equivalent form in another dialect) be in health, which was the form of drinking a health. The form wes is imperative. See Was, and Whole.