a consonant formed when the tongue rises toward the roof of the mouth and then retracts toward the back of the oral cavity
ˈɹɛtɹoˌflɛks] - adjective for things involving a curled-up tongue tip.- specifically: the place of articulation for sounds made with the tongue tip curled back to the postalveolar region or further.
(C): (manner of articulation). A sound characterized by positioning the tongue at the back of the alveolar ridge. English example: /r/.