U+01C3 Latin Letter Retroflex Click

The Wikipedia has the following information about this codepoint:

The alveolar or postalveolar clicks are a family of click consonants found only in Africa and in the Damin ritual jargon of Australia. The tongue is more or less concave (depending on the language), and is pulled down rather than back as in the palatal clicks, making a hollower sound than those consonants.

The symbol in the International Phonetic Alphabet that represents the place of articulation of these sounds is ⟨ǃ⟩. The symbol is not an exclamation mark in origin, but rather a vertical bar with a subscript dot, the dot being the old diacritic for retroflex consonants. Prior to 1989, ⟨ʗ⟩ (stretched c) was the IPA letter for the alveolar clicks, and this is still preferred by some phoneticians. The tail of ⟨ʗ⟩ may be the tail of retroflex consonants in the IPA, and thus analogous to the underdot of ⟨ǃ⟩. Either letter may be combined with a second letter to indicate the manner of articulation, though this is commonly omitted for tenuis clicks.

In official IPA transcription, the click letter is combined with a ⟨k ɡ ŋ q ɢ ɴ⟩ via a tie bar, though ⟨k⟩ is frequently omitted. Many authors instead use a superscript ⟨k ɡ ŋ q ɢ ɴ⟩ without the tie bar, again often neglecting the ⟨k⟩. Either letter, whether baseline or superscript, is usually placed before the click letter, but may come after when the release of the velar or uvular occlusion is audible. A third convention is the click letter with diacritics for voicelessness, voicing and nasalization; it does not distinguish velar from uvular alveolar clicks. Common alveolar clicks are:

The last can be heard in the sound sample at right; non-native speakers tend to glottalize clicks to avoid nasalizing them. The nasal click may also be heard at the right.

In the orthographies of individual languages, the letters and digraphs for alveolar clicks may be based on either the vertical bar symbol of the IPA, ⟨ǃ⟩, or on the Latin ⟨q⟩ of Bantu convention. Khoekhoe and most Bushman languages use the former; Naro, Sandawe, and Zulu use the latter.