rice bean Vigna umbellata, an annual legume of tropical Asian origin, so named because its small seeds, when dried, are eaten with or instead of rice and are only slightly larger than rice grains. Colour of the seeds ranges from yellow through red and brown to black, and the beans are sometimes mottled. Light-coloured types are preferred.
Rice beans have been grown extensively in NE India and adjoining regions as far east as southern parts of China. However, the quantities grown have diminished, partly because of changed patterns of rice production which have eliminated the intervals between rice crops, intervals in which it was formerly the practice to insert a crop of rice beans. Nevertheless, the fact that the rice bean is one of the very best legumes for nutritional purposes has recently caused a renewal of interest in its use as food for humans.