What is the meaning of ǂ?

the forward release of a palatal click.

the tenuis velar or sometimes uvular palatal click, [k͜ǂ] or [q͜ǂ]

[ǂ]-coloring or a weak, fleeting or epenthetic [ǂ]-release.

A letter of the Juǀ'hoan alphabet, written in the Latin script.

A letter of the Khoekhoe alphabet, written in the Latin script.

Source: wiktionary.org