Unless a term is defined in legislation or regulation in your area of operation, such terms can mean whatever the user chooses them to mean .. ie, one must ALWAYS refer to the document or supporting documents to find out what is in, or not in, the various operating weights.
Re the DC8 .. a google search showed up
this accident report which apparently has some weights for one such machine .. unfortunately, I am on a pretty slow connection tonight so I am not going to bother having a look at the report as it is a large-ish file download. ..