tremolo

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A tremulous effect produced by rapid repetition of a single tone.
2. n. A similar effect produced by rapid alternation of two tones.
3. n. A device on an organ for producing a tremulous effect.
4. n. A vibrato in singing, often excessive or poorly controlled.

Century Dictionary and Cyclopedia

1. n. In music:
2. n. A tremulous or fluttering effect in vocal music, intended to give a sentimental or passionate quality to the tone, but often carried to a pedantic and offensive extreme.
3. n. A similar effect in instrumental music, produced by a rapid reiteration of a tone or chord.
4. n. A similar effect in organ music, produced in the pipe-organ by means of a delicately balanced bellows attached to one of the wind-trunks, and in the reed-organ by a revolving fan.
5. n. The mechanical device in an organ by which a tremolo is produced; a tremulant. The use of such a mechanism is usually controlled by a stop-knob. Also tremolant, tremulant.

Wiktionary

1. n. music A rapid repetition of the same note, or an alternation between two or more notes. It can also be intended to mean a rapid and repetitive variation in pitch for the duration of a note. It is notated by a strong diagonal bar across the note stem, or a detached bar for a set of notes (or stemless notes).

GNU Webster's 1913

1. n. The rapid reiteration of tones without any apparent cessation, so as to produce a tremulous effect.
2. n. A certain contrivance in an organ, which causes the notes to sound with rapid pulses or beats, producing a tremulous effect; -- called also tremolant, and tremulant.

WordNet 3.0

1. n. (music) a tremulous effect produced by rapid repetition of a single tone or rapid alternation of two tones
2. n. vocal vibrato especially an excessive or poorly controlled one