Definition

Someone who's hopelessly uncool, out of touch, or boringly conventional—basically the human equivalent of beige wallpaper. A person so unhip they make your grandparents look edgy.

Example Usage

My dad refused to go to the concert because he needed to be home by 9 PM. Total square.

Source: Urban Dictionary (https://www.urbandictionary.com/define.php?term=square&defid=2266)