The voiceless retroflex flap or tap is a sound that has been reported to occur as a dialectal realization of /ʂ/ in the Dhivehi language.^[1] The symbol in the International Phonetic Alphabet that represents this sound is ⟨ɽ̊⟩, and the equivalent X-SAMPA symbol is r`_0.

Features of the voiceless retroflex flap:

• Its manner of articulation is tap or flap, which means it is produced with a single contraction of the muscles so that one articulator (usually the tongue) is thrown against another.
• Its place of articulation is retroflex, which prototypically means it is articulated subapical (with the tip of the tongue curled up), but more generally, it means that it is postalveolar without being palatalized. That is, besides the prototypical subapical articulation, the tongue can be apical (pointed) or, in some fricatives, laminal (flat).
• Its phonation is voiceless, which means it is produced without vibrations of the vocal cords. In some languages the vocal cords are actively separated, so it is always voiceless; in others the cords are lax, so that it may take on the voicing of adjacent sounds.
• It is an oral consonant, which means air is allowed to escape through the mouth only.
• It is a central consonant, which means it is produced by directing the airstream along the center of the tongue, rather than to the sides.
• The airstream mechanism is pulmonic, which means it is articulated by pushing air solely with the intercostal muscles and abdominal muscles, as in most sounds.