I am guilty of this myself in the past, but I never really liked this acronym. Most Viable Product or Most Valuable Product doesn't say to me that this is something useful. This term is probably the most abused term in industry and we throw it around like it is the solution to all of our problems. We like to start small and build big in the end, but starting with something small enough which has very little value to the user is a waste of 'valued time and resources'.
So, what should we use instead, you ask? We should be building real value for the user and not for the business. Essentially, if you build a prototype or sample working version of some solution, and it demonstrates your capabilities as a developer, architect or designer, that is all you have done. The business can see that you are the right person(s) to continue with the project, but you have not delivered real value to the end user.
When we prototype in design (rapid or other), we focus on the end user. What do they want, what do they need, and what will satisfy their urges for a strong user experience? How are we addressing their issues or pain points? This should be our focus. So I introduce the new acronym to your list: The MUP - Minimal Usable Product.
With this simple change of term, we can start to focus on creating value for the user and not just the business. Keep in mind, that a happy user feeds a successful business. Forget about demonstrating all the 'possible features' that the user might want, and instead, focus on delivering one or two 'real features' which users will want to use, reuse and give more valuable feedback into the next steps in your backlog to build the ideal solution or product .
In the future I hope to see less MVPs and more MUPs, which in turn will mean happier users, a more engaged business and a clearer vision of where this product will go.
Good luck! Although we are changing just one letter, it really is a change of mindset.
Image Source: http://blog.crisp.se/2016/01/25/henrikkniberg/making-sense-of-mvp
(MUP) is the minimum features that we need to build so that a user can use the product for the purpose it was intended