trill 
(trĭl)
(trĭl)n.
1. A fluttering or tremulous sound, as that made by certain birds; a warble.
2. Music
a. The rapid alternation of two tones either a whole or a half tone apart.
b. A vibrato.
3. Linguistics
a. A rapid vibration of one speech organ against another, as of the tongue against the alveolar ridge in Spanish rr.
b. A speech sound pronounced with such a vibration.
v. trilled, tril·ling, trills
v.tr.
1. To sound, sing, or play with a trill.
2. To articulate (a sound) with a trill.
v.intr.
To produce or give forth a trill.
[Italian trillo, from trillare, to trill, probably ultimately of imitative origin.]