1. (n.) A spirit (most often whiskey) mixed with a carbonated beverage in a roughly 1:2 ratio and served in a tall glass over ice. Originally a whisky and soda drink, the name supposedly originated with New York bartender Patrick Duffy in the late 19th century, but the simple mixture has ancestral roots in many a mixed drink, including fizzes and bucks.
2. (n.) a tall glass in which highball cocktails are served.