Sentence:  It is universally accepted that the <WSD>rhotacism</WSD>, 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 <WSD>rhotacism</WSD>. 
Meaning of the word marked with <WSD> tags:  Inability to pronounce the letter R; derhotacization.