The phrase "a completely ordinary" is correct and usable in written English.
It can be used to describe something that is entirely normal or typical, often to emphasize the lack of uniqueness or special qualities.
Example: "Despite the hype, the movie turned out to be just a completely ordinary romantic comedy."
Alternatives: "an entirely usual" or "a perfectly normal".
Her hair was brown, a completely ordinary brown.
above ten per cent, which is a completely ordinary performance by U.S. standards.
They see a masterpiece; I see a completely ordinary, amiably cartoonish and well aerated page-turner that does nothing interesting in literary terms at all.
It tells of "a completely ordinary wife" who decides to become a vegetarian as she seeks a more "plant-like" existence.
It was written in 1965 and concerns the life of a completely ordinary and undistinguished man, a university professor who no one much admires or even likes.
I was expecting from them, 'We knew, we had a sense, there was something eerie in the air.' But what they described was almost more tragic: a completely ordinary flight.
Write your diary in a completely ordinary-looking school notebook (you might even put school notes on the first few pages) and keep it with other school stuff.
His writing specializes in the exploration of the minor emotions often slighted by "serious" writers: contentment rather than elation, glumness rather than despair, horniness instead of passion, and, everywhere, a non-existential, completely ordinary loneliness.
Yes indeed, the Padres - a bland, vanilla and completely ordinary organization with little history of spending big on free agents are the champions of the offseason.
As a rule, he writes about completely ordinary people, middle- and working-class, from drab places.
Creating a hyggelig work environment is completely ordinary in Denmark – when I visited the ambassador to Britain, Claus Grube, he lit candles, switched off overhead lighting and put a cushion behind my back.
