yam bean n 1: twining plant of Amazon basin having large edible roots [syn: {yam bean}, {potato bean}, {Pachyrhizus tuberosus}] 2: Central American twining plant with edible roots and pods; large tubers are eaten raw or cooked especially when young and young pods must be thoroughly cooked; pods and seeds also yield rotenone and oils [syn: {yam bean}, {Pachyrhizus erosus}]