Uzboi Vallis is a valley lying situated within the Margaritifer Sinus quadrangle region on Mars. Uzboi Vallis is believed to have been formed by running water. It is believed that layers were formed on the floor when drainage was blocked by the impact that formed Holden Crater to the north. (wikipedia entry)
A vallis is a valley. On Mars large valles are named after words for Mars/star in various languages. Small valles are named after classical or modern names of rivers.