Water radish \Wa"ter rad"ish\ (Bot.) A coarse yellow-flowered plant ({Nasturtium amphibium}) related to the water cress and to the horse-radish.
Nasturtium amphibium n : perennial herb found on streams and riversides throughout Europe except extreme north and Mediterranean; sometimes placed in genus Nasturtium [syn: {great yellowcress}, {Rorippa amphibia}]