What is a "reference" system?

Good question.

Unfortunately, it is used in more than one way. The most common is a highly resolving high end system.

I used to have a system that I was forced to call my reference system because it was so revealing. The venue and mastering was so obvious instantly on hearing a cut. I felt obligated to call it my reference system. I had it for a long time and used it as a reference for components and my other systems. Interestingly, I now have a much better system, and I do not call it my reference system. It simply sounds like music. The venue and mastering are not unnaturally highlighted as they were in my reference system.  

Technically, any system can be a reference system if it is your semipermanent system you use to make judgements on new (to you) components or against other systems. This is a really useful way to think about your system.

Professional reviewers have their own system, which they know really well, and which they will swap components in order to assess them. This is their reference system... inexpensive or expensive. 

Reference is critical in assessing something for which there is not absolute reference. Since you can’t bring in a symphony to your listening location and compare it with your system... a reference is a very useful.  

My reference is live music, not a system. 

A "reference" system is usually understood as a system on which a man with a Medicare card spent obscene amounts of money.

A ‘Reference’ system has nothing to do with being the “best”, it states a system you are familiar with. A lot of manufacturers put ‘reference’ in the name of the product to try to boost sales. Just like ‘Signature’, what does that mean in reference to sq? Would you buy a component just because it states reference or signature?

My belief is "reference" implies one has more than one system, and the "reference" is the best one. That may be the most familiar, or most revealing system. If one has only one system then that must be their reference system, regardless of price or sound quality. 

Yes, I also do think it is ridiculous- seems like bragging to me. Would a reviewer test a product without putting it in the "reference system"? Obviously not, so why then explain to readers at the onset of the review  it was tested in the "reference system" ? Simply list the other components in the system it was used with.