There are several issues that I have gathered from your message:
0-It is not your job to manage the project and it is not your job to gather end-user requirements.
1-The boss does not know the exact requirements
2-The boss does not to talk to end-users about the requirements
3-The boss is throwing terminology he does not really understand agile
4-You are working out some solution that gets re-written several times and you are not happy about it
As for 1,2 and 3 there is little can be done about this if you are not a senior person. However, the following can be done:
A - Ask him to share with you the project plan. He may have one or will build one showing the tasks and deadlines. One of these should be about analysis and requirements gathering. If not suggest it.
B - Prepare some references on the importance of requirements to the success of software project
C - Prepare him a 1 page of what Agile is and is not.
D - Prepare him a list of typical inputs to the design stage and convince him of the value of each.
E - Suggest the addition of a business analyst and/or data modeler to the team. Such roles will have to sit with the end-user and will get you the information required or at least good part of it.
F - See how other developers cooped with this guy.
As for #4, you can suggest to him to use a prototyping approach or a code generator that would help him, you and the user to make their mind about the functional aspects of the application. Most tools don't generate perfect GUI, but at least you could capture the functionality required.
In all cases, make sure that you document each of the iterations clearly and send him an email about what input you have received, what you did (in some detail) and what the outcome is. Make sure you attribute the outcomes to the proper cause such as (lack of requirements, etc.).
Unfortunately some people don't accept advice. So be careful how you communicate with him.
This is not going well!