A twist is a piece of citrus zest used as a cocktail garnish, generally for decoration and to add flavor when added to a mixed drink.
There are a variety of ways of making and using twists. Twists are typically cut from a whole fresh fruit with a small kitchen knife immediately prior to serving, although a peeler, citrus zesters, or other utensil may be used. A curled shape may come from cutting the wedge into a spiral, winding it around a straw or other object, or as a byproduct of the cutting.
They are generally about 2 inches long (although length varies), and thin.