It is used in the orthographies of some African languages such as Ewe, and Shona from 1931 to 1955 to write [β], like the pronunciation of ⟨v⟩ in "van" using both lips.
In Mossi (Mooré) it is used to write [ʊ], like the pronunciation of ⟨oo⟩ in "foot".
In Kabiye and Ikposso it is used to write [u] (with retracted tongue root), like the pronunciation of ⟨oo⟩ in "food".
It is also used in the North American language Choctaw to write [ə], a schwa, like the pronunciation of ⟨a⟩ in "again".
[1] Its lowercase form, [ʋ], is used in the International Phonetic Alphabet for a labiodental approximant.