In defining smooth jazz I'm reminded of Chief Justice Stewart's definition of pornography "I know it when I see it". When I surf stations and encounter smooth jazz, my response is "wow, these musicians sound great, why do I hate this so much?... oh it's smooth jazz."
BTW, I was late teens/early 20's when Dave Grusin, Jeff Lorber, Tom Scott, Lee Rit became active and I loved the stuff then, not so much now. I did see Jeff Lorber play at Toad's Place; great show. I do appreciate the Richard T influence on Dave's electric grand solo.