Fann þetta á Wikipedia, Verst er semsagt það sama og röst.

A verst (Russian versta, верста) is an obsolete Russian unit of length. It is defined as being 500 sazhen long, which makes a verst equal to 3500 feet (1.0668 kilometres).

In the English language, verst is singular with the normal plural versts. In the Russian language, the plural for “versta” in genitive case usually used following numbers is “verst”: 10 verst, 25 verst, etc., which explains the origin of the English form of the word.

A mezhevaya verst (border verst) is twice as long as a verst.

Now verst is used colloquially as a synonym of kilometer.