Other forms: zesters
A zester is a kitchen tool that you use to take the outer part of a citrus fruit's rind off so that it can be used to flavor a dish.
The zest of a citrus fruit is the very outer, colored part of its skin, which holds a lot of flavor. But it's hard to just get the very top layer off the fruit, which is why there is a zester. This utensil usually has a handle and a head with small, sharp holes or teeth. By dragging the tool across the surface of a lemon, lime, or orange, the zest is shaved off in fine strands or tiny curls, leaving behind the bitter white pith.