What is the meaning of ʙ?

a bilabial trill.

[ʙ]-trilled release of a plosive (e.g. [b𐞄], sometimes implying an affricate [b͜ʙ]); or a weak, fleeting or epenthetic [ʙ].

partially-devoiced b (IPA [b̥]).

Used for lower-case 'b' in the Unified Northern Alphabet to avoid confusion with the vowel ь.

Used for lower-case 'b' in the Unified Northern Alphabet to avoid confusion with the vowel ь.

Used for lower-case 'b' in the Unified Northern Alphabet to avoid confusion with the vowel ь.

Phonetic transcription of sound [bⁿ].

Used for lower-case 'b' in the Unified Northern Alphabet to avoid confusion with the vowel ь.

Source: wiktionary.org