What is the meaning of ?

type: rhotic rhyme

general transliteration: er

keyboard key: -

34th letter of the Zhuyin alphabet

56th letter of the extended Zhuyin alphabet

Sound IPA: /ɻ/ (Pinyin: er), which is present only in Mandarin and Wu.

Sound IPA: /ˀɤɻ/ (Pinyin: er)

43rd letter of the Hmu Zhuyin alphabet.

Source: wiktionary.org