—n.
1 a quavering or vibratory sound, esp. a rapid alternation of sung or played notes.
2 a bird's warbling sound.
3 the pronunciation of r with a vibration of the tongue.
—v.
1 intr. produce a trill.
2 tr. warble (a song) or pronounce (r etc.) with a trill.
Etymology: It. trillo (n.), trillare (v.)
Useful english dictionary. 2012.