ɾ

Etymology
A turned small-capital J (turned ᴊ), from the era when printers generally created new phonetic symbols turning metal type of existing letters upside-down. The name in English is "fishhook R".

The Karlgren letter ɿ is unrelated.

Symbol

 * 1)  an alveolar flap or tap.
 * 2)  a flapped -release, -coloring, or a weak, fleeting or epenthetic.