<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Rut Dog:
OK, maybe it has to do with the type of room being subject to change? But usually that says something like "best available room at check in".</font>
"Best available", huh?
In a situation you describe, it usually says either "Run of the House", or just "Guest Room", which means that you are not guaranteed any particular room type.
That "Flexible Rate" notation most likely means that the rate is fully cancellable, etc. I see this term being used occasionally, but typically at non-US properties. It is lower than the "Rack Rate", and the difference is that "Rack Rate" is fixed, and "Flexible Rate" changes with supply and demand.