Ciro Santilli defines "Smooth Jazz" simply as jazz that he can leave on the background to work without being particularly distracted.
It does not mean that the music is bad in any way. Just not particularly distracting.
Ciro Santilli's "Soft Jazz" YouTube playlist: www.youtube.com/playlist?list=PLcZOZrP1P_V4Sxz8y1JLKLbZOv3GLb_Xf
List:
- Page One by Joe Henderson (1963)