any of several plants of the genus Saponaria (about 40 species), in the pink family (Caryophyllaceae). While most are weedy, a few are cultivated, especially the trailing species S. ocymoides, with several varieties having pink to deep-red flower clusters. Bouncing Bet (S. officinalis), reaching to a height of 1 metre (3 feet), is widely naturalized in eastern North America. Its roots have been used medicinally, and its sap is a substitute for soap.