oka
noun
less common spelling of oca
: either of two South American wood sorrels (Oxalis crenata and O. tuberosa) cultivated for their edible tubers
also : the tuber of an oca
Geographical Definition
Oka
geographical name
ō-ˈkä 
1
river 530 miles (853 kilometers) long in south central Russia in Asia flowing north from the Sayan Mountains into the Angara River
2
river 919 miles (1479 kilometers) long in central Russia in Europe flowing into the Volga River