A spicy ingredient to put in your salad. Known to botany as Eruca vesicaria; known to most of the English-speaking world as rocket (see Sneff's excellent writeup there).

If you have some arugula and don't know what to do with it, you can mix it in with other salad greens; Footprints has a very good recipe for an arugula-based Green Salad with Goat Cheese, Walnuts and Hot Onions.