I'm afraid I'm going to be controversial again. I think, upon investigation, it will be found that 'secular' does not mean 'non-christian' when used by christians, as a rule. That does not, of course, cover everyone's use of the word. It could even be that people of other faiths use 'secular' to mean non-christian too, but that is news to me. Thank you for the information, elsie-joy. It does clear up something in your original post that I was puzzled about. One of the first lessons I had in philosophy at university was about defining the words one was using. It has been shown on this thread how important this is for preventing misunderstandings.
I will, however, stick with the dictionary definitions for my own use. Just wanted to make that clear. I might refer to a christian as secular, you see, and I won't be insulting them if I do.