What is the meaning of ʂ?

a voiceless retroflex sibilant.

[ʂ]-fricated release of a plosive (e.g. [tᶳ] or [ʈᶳ]), sometimes implying an affricate (e.g. ʈᶳ for [ʈ͡ʂ]); [ʂ]-coloring; or a weak, fleeting or epenthetic [ʂ].

A letter of the draft Pinyin alphabet of the 1950s; used to represent /ʂ/ and corresponds to modern ⟨sh⟩.

Source: wiktionary.org