Nasal retroflex click
The retroflex nasal click is a rare click consonant. In practical orthography, an ad hoc symbol  is used for the retroflex clicks; a nasal click with a velar rear articulation is  or , commonly abbreviated to ,  or . The implicit symbol in the International Phonetic Alphabet is  or , abbreviated ,  or . Linguists who prefer the old IPA letters use the analogous Doke convention of  or , abbreviated ,  or . For a click with a uvular rear articulation, the equivalents are ,  and . Sometimes the accompanying letter comes after the click letter, e.g. or ; this may be a simple orthographic choice, or it may imply a difference in the relative timing of the releases. Features
Features of the retroflex nasal click:

Occurrence
Retroflex nasal clicks are only attested from two languages, Central !Kung and Damin. Glottalized alveolar nasal click

All Khoisan languages have glottalized nasal clicks. These are formed by closing the glottis so that the click is pronounced in silence; however, any preceding vowel will be nasalized. References

Nasal consonants
Palatal consonants
Click consonants
Central consonants
Voiced consonants