The Boomerang cocktail is a style of cocktail that was popular in the mid-20th century. Recipes vary widely, but often include whiskey and vermouth, lemon juice, and Angostura bitters. Most recipes include a sweetener, which ranges from Maraschino liqueur to Swedish punsch.
The term Boomerang cocktail is also, occasionally, bartender jargon for the practice of sending drinks between bartenders at competing bars.