An old Finnish unit of length. Allegedly the word means the distance a reindeer ("poro" in Finnish) can run without taking a leak on the way ("kusi" is a dirtyish word for urine). The exact measure of this distance is hard to come by since the unit is very old but according to an article in a Finnish newspaper it is about 7.5 kilometers. If someone is interested enough to carry out an empirical study about this, please inform me about the results.