1. (v.) A bartending skill used to layer cocktail ingredients in the glass, as seen in drinks such as the New York Sour or Pousse Café. Typically a bartender will pour the heavier liquid in the glass first, then slowly pour the second liquid into the glass over the back of a bar spoon so that the second component floats on top of the first.
2. (n.) A tall, fizzy beverage poured over scoop of ice cream, such with as a Root Beer Float.