1.a sound, especially a speech sound, that does not rise or fall in pitch, but stays on the same tone all the time
2.a sequence of sounds, e.g. a piece of speech, singing, or music, that stays at exactly the same pitch throughout
3.a complete lack of variety in color, expression, or style
4.somebody who cannot produce or distinguish between sounds of varying pitches when singing
5.a way of talking that is boring because your voice does not change in loudness or become higher or lower