Absolute Reality is something that is a fact, i.e., a concept, statement, thing, scientific law, or event that can been unequivocally (indisputably) proven to be true. Facts are always based on concrete verified evidence which substantiate their truth. Absolute Reality is mind-independent, i.e. it would continue to be the case whether or not anyone believed it, or indeed whether or not there were any minds to believe it in the first place.
"That which, when you stop believing in it, doesn't go away." -- Philip K. Dick