n.
 a quavering or vibratory sound, especially a rapid alternation of sung or played notes. 
▸the pronunciation of a consonant, especially r, with rapid vibration of the tongue against the hard or soft palate or the uvula.
v.
 produce or pronounce with a trill.
Derivative
  
  Etymology
  C17: from Ital. trillo (n.), trillare (v.).