Flumen (planetary geology)
Flumen  (plural flumina) is the Latin word for river. It is used in planetary geology to name landform features on the Saturnian moon Titan. A flumen is a channel on Titan that may carry liquid (usually hydrocarbons, like methane and ethane). Systems of linear, channel-like features on Titan are called flumina. Examples include Vid Flumina, a river of liquid methane and ethane about 400 km long, and Elivagar Flumina, a network of river channels in the region around the Menrva Crater of Titan. References 

Planetary geology
Surface features of Titan (moon)