I have no idea what you mean by this. I explained in detail what changing one's mind entails. It has nothing to do with "irrefutable" or deeply held convictions.
You have a nonstandard definition of belief.
First of all, "I don't know" is absolutely a state of acceptance. It is acceptance that the information is not fully reliable. Most things are unknowable; the vast majority of held beliefs are not arrived at through irrefutable logic but by simple trust in consensus. I believe that certain food is nutritious, even though I have not run tests on it myself. Data might arise later showing my beliefs to be false; that is why I assign probabilities to my beliefs, rather than certainties.
Second of all, your fallback to a dictionary definition is flawed in two ways. The first is that various definitions of "belief" exist; one of which (from https://www.wordnik.com/words/belief) is "Assent to a proposition or affirmation, or the acceptance of a fact, opinion, or assertion as real or true, without immediate personal knowledge; reliance upon word or testimony; partial or full assurance without positive knowledge or absolute certainty; persuasion; conviction; confidence." (emphasis added) Another definition given is "A conviction of the truth of a given proposition or an alleged fact, resting upon grounds insufficient to constitute positive knowledge."
The second way this argument is flawed is that dictionaries are descriptive tools, not prescriptive. That is to say, dictionaries are not arbiters of truth in language but merely reference documents for possible meaning, and where they differ from common usage, it is the dictionary that is incorrect.