The word "khoum" is a noun that refers to a specific currency unit used in Mauritania, a country in West Africa. In this context, 5 khoums equal 1 ouguiya, which is the main currency of Mauritania.
In summary, "khoum" is a currency unit in Mauritania where 5 khoums make up 1 ouguiya. It is primarily used when talking about money and prices in that region.