What is the meaning of ʃ?

a voiceless palatoalveolar sibilant.

[ʃ]-fricated release of a plosive (e.g. [tᶴ], sometimes implying an affricate [t͜ʃ]); [ʃ]-coloring; or a weak, fleeting or epenthetic [ʃ].

voiced alveolar fricative (/z/)

Obsolete letter formerly used to represent the phoneme /ʃ/. Replaced by sh.

Source: wiktionary.org