(n.) An object placed on or in a finished cocktail that performs a decorative function, though some may also add flavor. Many garnishes are built into traditional cocktail recipes; some have even come to distinguish one cocktail from another, such as the cocktail onion, which turns a Martini into a Gibson.  Candidates for adornment include edible items, such as slices of citrus, shaved citrus peel, olives or cherries, as well as ornamental flourishes, such as mini-paper cocktail umbrellas.

2. (v.) The act of placing a garnish on a drink.