noun

1. The sound of one who warbles; singing with trills or modulations.

2. In naval mine warfare, the process of varying the frequency of sound produced by a narrowband noisemaker to ensure that the frequency to which the mine will respond is covered.

verb

1. To modulate a tone's frequency.

2. To sing like a bird, especially with trills.

3. To cause to quaver or vibrate.

Synonyms: trill