The bilabial trill is a type of consonantal sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ʙ, and the equivalent X-SAMPA symbol is B\.
Features of the bilabial trill:
English does not have the bilabial trill as a phoneme.
In other languages
The bilabial trill exists as a phoneme in a few languages. In most, if not all, of the languages where it occurs, it should probably more exactly be analysed
as a prenasalised stop with trilled release.
Some languages, such as Mangbetu (spoken in North-Eastern Zaire) and Mewun (spoken in Vanuatu), may have both voiced and voiceless bilabial trill.
In Abkhaz, the "affricate" [tʙ] is an allophone of /tw/.
Amuzg has the bilabial trill, but uses it only exceptionally.
Baka (spoken in Vanuatu) has the bilabial trill, but it is used rarely.
In Pirahã, the bilabial trill is an allophone of /b/.
Some dialects of Yi have /ʙ/ as a phoneme.