Non-electronic music; that is, made without the use of electric guitars, synthesizers, drum machines, vocoders, etc.

Music can certainly be recorded using electronics and still be considered acoustic; the point is that the music heard when you play back the recording should be as close as possible to what you would have heard if you had been there live.

Many musicians have always played acoustic music and think it odd that there should need to be a special name for it. Others have always made electronic music and can't imagine having to use just one or two textures and being forbidden to use loops.