it is used to descirbe people that are really " seven" it means that they are very uncool. obsviously that are UGly, bad looking and no sense of style.
noun, adjective - seven.
seven is upon those people.
you dont' say sevenism it's used to describe those type of people. in actual stituation you say, " You're so SEVEN" which means You're very ugly, nasty, styleless, bad looking , unwanted.