By definition, dictionaries are always playing catch-up. Sometimes they take it slowly, sometimes fast, but they are always a yard or two off the pace. They are for ever recording what people have already meant by the words they speak and write. They can never say, 'From now on, this is what you must mean by using this word'.
So we cannot always expect them to know what Christians are talking about. Especially when we hardly know ourselves. These deep thoughts are stirred by the way we use the language of songs.
What, for instance, is or was a Gospel song? They have been around for a century or so. My 1995 Dictionary has not discovered them yet, though it does recognise 'Gospel Music'. Let me try some descriptions which may fall an inch or two short of definitions, but may help to fill the 'Letters' page for a couple of months.