In phonetics and phonology, a retroflex stop is a type of consonantal sound, made with the tongue curled back and in contact with area behind the alveolar ridge or with the hard palate (hence retroflex), held tightly enough to block the passage of air (hence a stop consonant).
That is known as a subapical retroflex stop and particularly occurs in the Dravidian languages of southern India.
They sound somewhat like the native English alveolar stops [t] and [d], but they have a more hollow quality.
Although they are fairly rare in European languages, they occur in Swedish and Norwegian, as well as in some Southern dialects of Italy, such as in varieties of Sicilian, Calabrian, and Sardinian.
More generally, several kinds are distinguished: Symbols to the right in a cell are voiced, to the left are voiceless.