The teacher taught the students how to roll their r's when speaking Spanish.
Учитель научил студентов картавить, когда они говорят на испанском.
Definitionen
To pronounce the letter 'r' with a trilled or rolled sound, typically by vibrating the tongue against the roof of the mouth. This is common in languages like Spanish or Italian. The phrase can also refer to someone's ability or inability to make this sound.