It is ordinary because we are able to directly observe it with one or more of our five senses and process the sensory inputs with various parts of our nervous system. That implies a few things which are less obvious. For one, only those aspects of reality detectable to our five senses are real in the Ordinary Reality sense. Non-ordinary means are necessary to establish the reality of things like X-rays, ultraviolet or infrared "colors," the vast majority of odors all dogs easily smell, the mechanical impact of ultra light things such as individual molecules of air, the ultrasonic sounds that set the dogs howling, the invisible passing of a speeding bullet arriving before its sound, the growing of an ancient tree or the drifting of the continents, almost imperceptible in a human lifetime, and until very recently the curvature of an Earth so obviously flat. Just about anything a million times bigger or smaller, faster or slower, louder or quieter, hotter or colder than the ordinary human experience of space, time and energy fall outside Ordinary Reality. 

Well! So what? The answer is that almost everything falls outside those dimensions! What we experience is the exception! And, our Ordinary Reality is not very ordinary at all when viewed from cosmic or sub-atomic scales. Take a look at this dramatic demonstration of our relationship to orders of magnitude in the Universe (Florida State University-Tallahassee) or this mind boggling series of illustrations showing the relative sizes of objects in the visible universe. In our ordinary day to day lives it is the directly observable which makes up our common-sense consensual reality. Notice I sneaked in the idea of consensus, because we each experience ordinary reality from our own unique personal perspective. Dramatically divergent aspects among our Personal Realities lead to some surprising consequences for us individually which I will examine in the next section.