ground plum

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A perennial plant (Astragalus crassicarpus) of the central and western United States, having compound leaves, purple or white flowers, and green, plumlike, edible fruit.
2. n. The fruit of this plant.

GNU Webster's 1913

1. n. (Bot.) a leguminous plant (Astragalus caryocarpus) occurring from the Saskatchewan to Texas, and having a succulent plum-shaped pod.