garden cress

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An annual herb (Lepidium sativum) of the mustard family, having pungent leaves and usually grown as a salad plant.

Wiktionary

1. n. a plant, Lepidium sativum, whose pungent leaves are used in salads

WordNet 3.0

1. n. cress cultivated for salads and garnishes