rhotacism

noun

1. (countable, uncountable)An exaggerated use of the sound of the letter R.
2. (countable)A linguistic phenomenon in which a consonant changes into an R; rhotacization.
3. (countable, uncountable)The inability to pronounce the letter R; derhotacization.

   “For example: r’s may become burrs or guttural grunts or w’s or l’s (rhotacism); […]”

   “From the analysis of Kana writings, hypothesizes that the inability to establish a stable… […] The correction of rhotacism by means of an electric vibrator.”

   “It is universally accepted that the rhotacism, a defective utterance of the /r/ sounds, is usually the last and most difficult American English consonant to correct functionally. I use two methods to help correct the rhotacism.”